tidy-up: miscellaneous

- drop more uses of the word "just". (not enforced here)
- drop some uses of the "will" word.
- "then" -> "than".
- tests/http/testenv/curl.py: fix copy-paste typo in error message.
- pytest: replace `shutdownh` with `shutdown` in test names.
  Spotted by GitHub Code Quality.
- comment typos.
- whitespace and newlines fixes.

Closes #21830

scripts/mdlinkcheck

@@ -108,7 +108,7 @@ sub storelink {
             #print "-- whitelisted: $link\n";
             $whitelist{$link}++;
         }
-        # example.com is just example
+        # example.com is used as example
         elsif($link =~ /^https:\/\/(.*)example.(com|org|net)/) {
             #print "-- example: $link\n";
         }