git-submodule.sh: remove unused sanitize_submodule_env()

The sanitize_submodule_env() function was last used before
b3c5f5cb04 (submodule: move core cmd_update() logic to C,
2022-03-15), let's remove it.

This also allows us to remove clear_local_git_env() from
git-sh-setup.sh. That function hasn't been documented in
Documentation/git-sh-setup.sh, and since 14111fc492 (git: submodule
honor -c credential.* from command line, 2016-02-29) it had only been
used in the sanitize_submodule_env() function being removed here.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-sh-setup.sh

@@ -285,13 +285,6 @@ get_author_ident_from_commit () {
 	parse_ident_from_commit author AUTHOR
 }
 
-# Clear repo-local GIT_* environment variables. Useful when switching to
-# another repository (e.g. when entering a submodule). See also the env
-# list in git_connect()
-clear_local_git_env() {
-	unset $(git rev-parse --local-env-vars)
-}
-
 # Generate a virtual base file for a two-file merge. Uses git apply to
 # remove lines from $1 that are not in $2, leaving only common lines.
 create_virtual_base() {

git-submodule.sh

@@ -56,17 +56,6 @@ isnumber()
 	n=$(($1 + 0)) 2>/dev/null && test "$n" = "$1"
 }
 
-# Sanitize the local git environment for use within a submodule. We
-# can't simply use clear_local_git_env since we want to preserve some
-# of the settings from GIT_CONFIG_PARAMETERS.
-sanitize_submodule_env()
-{
-	save_config=$GIT_CONFIG_PARAMETERS
-	clear_local_git_env
-	GIT_CONFIG_PARAMETERS=$save_config
-	export GIT_CONFIG_PARAMETERS
-}
-
 #
 # Add a new submodule to the working tree, .gitmodules and the index
 #