tests: fix patching test for no-compat mode

Closes Homebrew/homebrew#41977.

Signed-off-by: Xu Cheng <xucheng@me.com>

Library/Homebrew/formula.rb

@@ -941,7 +941,7 @@ class Formula
   end
 
   def prepare_patches
-    active_spec.add_legacy_patches(patches)
+    active_spec.add_legacy_patches(patches) if respond_to?(:patches)
 
     patchlist.grep(DATAPatch) { |p| p.path = path }
 

Library/Homebrew/test/test_patching.rb

@@ -106,7 +106,7 @@ class PatchingTests < Homebrew::TestCase
   def test_patch_DATA_constant
     assert_patched formula("test", Pathname.new(__FILE__).expand_path) {
       def patches
-        Formula::DATA
+        :DATA
       end
     }
   end