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/http-server.pl

@@ -40,7 +40,7 @@ use serverhelp qw(
     );
 
 my $verbose = 0;     # set to 1 for debugging
-my $port = 8990;     # just a default
+my $port = 8990;     # a default
 my $unix_socket;     # location to place a listening Unix socket
 my $ipvnum = 4;      # default IP version of http server
 my $idnum = 1;       # default http server instance number