put gtk3 < 0.14 in stackage upperbounds (#725)

build-constraints.yaml

@@ -1246,6 +1246,9 @@ packages:
         # https://github.com/fpco/stackage/issues/710
         - fsnotify < 0.2
 
+        # https://github.com/fpco/stackage/issues/725
+        - gtk3 < 0.14
+
 # Package flags are applied to individual packages, and override the values of
 # global-flags
 package-flags:
@@ -1662,8 +1665,7 @@ expected-haddock-failures:
     # Requires build before haddock, which doesn't always happen in incremental
     # builds. Could consider special-casing this requirement.
     - gtk
-    # https://github.com/fpco/stackage/issues/725
-    - gtk3 < 0.14
+    - gtk3
 
     # Not sure why, but it's a temporary package anyway
     - Cabal-ide-backend