Trim examples

docs/topics/debug.rst

@@ -16,7 +16,6 @@ Consider the following Scrapy spider below:
 
     class MySpider(scrapy.Spider):
         name = "myspider"
-        allowed_domains = ["example.com"]
         start_urls = (
             "http://example.com/page1",
             "http://example.com/page2",

docs/topics/logging.rst

@@ -113,7 +113,6 @@ instance, which can be accessed and used like this:
 
     class MySpider(scrapy.Spider):
         name = "myspider"
-        allowed_domains = ["scrapy.org"]
         start_urls = ["https://scrapy.org"]
 
         def parse(self, response):
@@ -132,7 +131,6 @@ Python logger you want. For example:
 
     class MySpider(scrapy.Spider):
         name = "myspider"
-        allowed_domains = ["scrapy.org"]
         start_urls = ["https://scrapy.org"]
 
         def parse(self, response):

docs/topics/request-response.rst

@@ -325,7 +325,6 @@ credentials:
 
     class LoginSpider(scrapy.Spider):
         name = "example.com"
-        allowed_domains = ["www.example.com"]
         start_urls = ["http://www.example.com/users/login.php"]
 
         def parse(self, response):
@@ -567,7 +566,6 @@ the crawl:
 
     class BookSpider(Spider):
         name = "books"
-        allowed_domains = ["books.toscrape.com"]
 
         async def start(self):
             yield Request("https://books.toscrape.com/", callback=self.parse_home)
@@ -785,7 +783,6 @@ errors if needed:
 
     class ErrbackSpider(Spider):
         name = "errback_example"
-        allowed_domains = ["www.httpbin.org", "example.invalid"]
         start_urls = [
             "http://www.httpbin.org/",  # HTTP 200 expected
             "http://www.httpbin.org/status/404",  # Not found error
@@ -1051,7 +1048,6 @@ signals will stop the download of a given response. See the following example:
 
     class StopSpider(scrapy.Spider):
         name = "stop"
-        allowed_domains = ["docs.scrapy.org"]
         start_urls = ["https://docs.scrapy.org/en/latest/"]
 
         @classmethod

docs/topics/settings.rst

@@ -217,7 +217,6 @@ In a spider, settings are available through ``self.settings``:
 
     class MySpider(scrapy.Spider):
         name = "myspider"
-        allowed_domains = ["example.com"]
         start_urls = ["http://example.com"]
 
         def parse(self, response):
@@ -2231,7 +2230,6 @@ In order to use the reactor installed by Scrapy:
 
     class QuotesSpider(scrapy.Spider):
         name = "quotes"
-        allowed_domains = ["quotes.toscrape.com"]
 
         def __init__(self, *args, **kwargs):
             self.timeout = int(kwargs.pop("timeout", "60"))
@@ -2261,7 +2259,6 @@ which raises an exception, becomes:
 
     class QuotesSpider(scrapy.Spider):
         name = "quotes"
-        allowed_domains = ["quotes.toscrape.com"]
 
         def __init__(self, *args, **kwargs):
             self.timeout = int(kwargs.pop("timeout", "60"))

docs/topics/shell.rst

@@ -262,7 +262,6 @@ Here's an example of how you would call it from your spider:
 
     class MySpider(scrapy.Spider):
         name = "myspider"
-        allowed_domains = ["example.com", "example.org", "example.net"]
         start_urls = [
             "http://example.com",
             "http://example.org",

docs/topics/signals.rst

@@ -26,7 +26,6 @@ Here is a simple example showing how you can catch signals and perform some acti
 
     class DmozSpider(Spider):
         name = "dmoz"
-        allowed_domains = ["dmoz.org"]
         start_urls = [
             "http://www.dmoz.org/Computers/Programming/Languages/Python/Books/",
             "http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/",
@@ -68,7 +67,6 @@ Let's take an example using :ref:`coroutines <topics-coroutines>`:
 
     class SignalSpider(scrapy.Spider):
         name = "signals"
-        allowed_domains = ["quotes.toscrape.com"]
         start_urls = ["https://quotes.toscrape.com/page/1/"]
 
         @classmethod