remove colour field patch (#6280)

Author: riknoll

package.json

@@ -47,19 +47,5 @@
     "dependencies": {
         "pxt-common-packages": "12.3.30",
         "pxt-core": "11.4.24"
-    },
-    "overrides": {
-        "@blockly/field-colour": {
-            "blockly": "^12.0.0-beta.4"
-        },
-        "@blockly/plugin-workspace-search": {
-            "blockly": "^12.0.0-beta.4"
-        },
-        "@blockly/keyboard-navigation": {
-            "blockly": "^12.0.0-beta.4"
-        }
-    },
-    "scripts": {
-        "postinstall": "node ./scripts/patchBlocklyFieldColour.js"
     }
 }