Rename STRV_MAKE_EMPTY to just STRV_EMPTY

Even though this creates a stack allocation, it is not a function macro, so
drop the "make" from the name.

src/test/test-string-util.c

@@ -496,7 +496,7 @@ TEST(foreach_word_quoted) {
               true);
 
         check("test\\",
-              STRV_MAKE_EMPTY,
+              STRV_EMPTY,
               true);
 }