gh-100519: simplification to eff_request_host in cookiejar.py (#99588)

`IPV4_RE` includes a `.`, and the `.find(".") == -1` included here is already testing to make sure there's no dot, so this part of the expression is tautological. Instead use more modern `in` syntax to make it clear what the check is doing here. The simplified implementation more clearly matches the wording in RFC 2965.

Co-authored-by: hauntsaninja <[email protected]>

Author: glyph

Lib/http/cookiejar.py

@@ -640,7 +640,7 @@ def eff_request_host(request):
 
     """
     erhn = req_host = request_host(request)
-    if req_host.find(".") == -1 and not IPV4_RE.search(req_host):
+    if "." not in req_host:
         erhn = req_host + ".local"
     return req_host, erhn
 

Misc/NEWS.d/next/Library/2022-12-24-16-39-53.gh-issue-100519.G_dZLP.rst

@@ -0,0 +1,2 @@
+Small simplification of :func:`http.cookiejar.eff_request_host` that
+improves readability and better matches the RFC wording.