t: avoid git config syntax from newer releases

In a recent security release, 05e9cd6 (config: quote values
containing CR character, 2025-05-19) added calls to `git config get`,
`git config set`, and `git config unset` which are not present on the
maint-2.43 branch.

These subcommands were added in the following commits, released in
git-2.46.0:

  4e51389 (builtin/config: introduce "get" subcommand, 2024-05-06),
  00bbdde (builtin/config: introduce "set" subcommand, 2024-05-06),
  95ea69c (builtin/config: introduce "unset" subcommand, 2024-05-06)

Revert to the previous `git config` syntax for older maintenance
branches.

Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: tmzullinger

t/t1300-config.sh

@@ -2595,8 +2595,8 @@ test_expect_success 'writing value with trailing CR not stripped on read' '
 
 	printf "bar\r\n" >expect &&
 	git init cr-test &&
-	git -C cr-test config set core.foo $(printf "bar\r") &&
-	git -C cr-test config get core.foo >actual &&
+	git -C cr-test config core.foo $(printf "bar\r") &&
+	git -C cr-test config --get core.foo >actual &&
 
 	test_cmp expect actual
 '

t/t7450-bad-git-dotfiles.sh

@@ -362,10 +362,10 @@ test_expect_success SYMLINKS,!WINDOWS,!MINGW 'submodule must not checkout into d
 	git -C repo mv sub $(printf "sub\r") &&
 
 	# Ensure config values containing CR are wrapped in quotes.
-	git config unset -f repo/.gitmodules submodule.sub.path &&
+	git config --unset -f repo/.gitmodules submodule.sub.path &&
 	printf "\tpath = \"sub\r\"\n" >>repo/.gitmodules &&
 
-	git config unset -f repo/.git/modules/sub/config core.worktree &&
+	git config --unset -f repo/.git/modules/sub/config core.worktree &&
 	{
 		printf "[core]\n" &&
 		printf "\tworktree = \"../../../sub\r\"\n"