recipeutils-test: use a small dependency in the dummy recipe

recipeutils-test: use a small dependency in the dummy recipe

recipeutils-test has virtual/libx11 as a DEPENDS, but this will cause errors if
the recipe is built in an environment without x11 in DISTRO_FEATURES.

This dependency isn't actually used for anything so we could remove it, but to
save updating the test cases too just swap virtual/libx11 for zlib.

[ YOCTO #13611 ]

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>