Limit Python 2.6 units to modules & module_utils. (#57377)

test/utils/shippable/units.sh

@@ -15,5 +15,14 @@ fi
 
 ansible-test env --timeout "${timeout}" --color -v
 
+if [[ "${version}" = "2.6" ]]; then
+    # Python 2.6 is only supported for modules and module_utils.
+    # Eventually this logic will move into ansible-test itself.
+    targets=("test/units/(modules|module_utils)/")
+else
+    targets=("test/units/")
+fi
+
 # shellcheck disable=SC2086
 ansible-test units --color -v --docker default --python "${version}" ${COVERAGE:+"$COVERAGE"} ${CHANGED:+"$CHANGED"} \
+    "${targets[@]}" \