Revert "test: fix t7001 cp to use POSIX options"

This reverts commit 00764ca, as our ancient version of "cp" has
problems about the "new" POSIX option "-P" (yields exit code 1).

Author: kasal

t/t7001-mv.sh

@@ -308,7 +308,7 @@ test_expect_success 'git mv moves a submodule with a .git directory and no .gitm
 	(
 		cd sub &&
 		rm -f .git &&
-		cp -R -P -p ../.git/modules/sub .git &&
+		cp -a ../.git/modules/sub .git &&
 		GIT_WORK_TREE=. git config --unset core.worktree
 	) &&
 	mkdir mod &&
@@ -331,7 +331,7 @@ test_expect_success 'git mv moves a submodule with a .git directory and .gitmodu
 	(
 		cd sub &&
 		rm -f .git &&
-		cp -R -P -p ../.git/modules/sub .git &&
+		cp -a ../.git/modules/sub .git &&
 		GIT_WORK_TREE=. git config --unset core.worktree
 	) &&
 	mkdir mod &&