fixup! tests: add a special setup where stash.useBuiltin is off

For some reason, this double-mention of the GIT_TEST_STASH_BUILTIN
variable crept in... Let's revert it.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

t/README

@@ -388,10 +388,6 @@ GIT_TEST_STASH_USE_BUILTIN=<boolean>, when false, disables the
 built-in version of git-stash. See 'stash.useBuiltin' in
 git-config(1).
 
-GIT_TEST_STASH_USE_BUILTIN=<boolean>, when false, disables the
-built-in version of git-stash. See 'stash.useBuiltin' in
-git-config(1).
-
 GIT_TEST_ADD_I_USE_BUILTIN=<boolean>, when true, enables the
 builtin version of git add -i. See 'add.interactive.useBuiltin' in
 git-config(1).