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

tests/sshserver.pl

@@ -1190,7 +1190,7 @@ if($sshdid =~ /OpenSSH-Windows/) {
     # new process to the parent waiting perl.exe and sh.exe processes.
 
     # exec() should never return back here to this process. We protect
-    # ourselves by calling die() just in case something goes really bad.
+    # ourselves by calling die() in case something goes really bad.
     die "error: exec() has returned";
 }