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/cd2nroff

@@ -426,7 +426,7 @@ sub single {
             print STDERR "$f:$line:1:ERROR: un-escaped < or > used\n";
             $errors++;
         }
-        # convert backslash-'<' or '> to just the second character
+        # convert backslash-'<' or '> to the second character
         $d =~ s/\\([<>])/$1/g;
 
         # mentions of curl symbols with man pages use italics by default