chore: Remove MDC form field screenshot test files (#5545)

Author: abhiomkar

test/screenshot/golden.json

@@ -231,22 +231,6 @@
       "desktop_windows_ie@11": "https://storage.googleapis.com/mdc-web-screenshot-tests/advorak/2018/09/26/06_08_27_877/spec/mdc-elevation/mixins/mixins.html.windows_ie_11.png"
     }
   },
-  "spec/mdc-form-field/classes/baseline-radio-rtl.html": {
-    "public_url": "https://storage.googleapis.com/mdc-web-screenshot-tests/travis/2019/09/10/20_51_43_383/spec/mdc-form-field/classes/baseline-radio-rtl.html?utm_source=golden_json",
-    "screenshots": {
-      "desktop_windows_chrome@77": "https://storage.googleapis.com/mdc-web-screenshot-tests/travis/2019/09/10/20_51_43_383/spec/mdc-form-field/classes/baseline-radio-rtl.html.windows_chrome_76.png",
-      "desktop_windows_firefox@69": "https://storage.googleapis.com/mdc-web-screenshot-tests/travis/2019/09/10/20_51_43_383/spec/mdc-form-field/classes/baseline-radio-rtl.html.windows_firefox_69.png",
-      "desktop_windows_ie@11": "https://storage.googleapis.com/mdc-web-screenshot-tests/travis/2019/09/10/20_51_43_383/spec/mdc-form-field/classes/baseline-radio-rtl.html.windows_ie_11.png"
-    }
-  },
-  "spec/mdc-form-field/classes/baseline-radio.html": {
-    "public_url": "https://storage.googleapis.com/mdc-web-screenshot-tests/travis/2019/09/10/20_51_43_383/spec/mdc-form-field/classes/baseline-radio.html?utm_source=golden_json",
-    "screenshots": {
-      "desktop_windows_chrome@77": "https://storage.googleapis.com/mdc-web-screenshot-tests/travis/2019/09/10/20_51_43_383/spec/mdc-form-field/classes/baseline-radio.html.windows_chrome_76.png",
-      "desktop_windows_firefox@69": "https://storage.googleapis.com/mdc-web-screenshot-tests/travis/2019/09/10/20_51_43_383/spec/mdc-form-field/classes/baseline-radio.html.windows_firefox_69.png",
-      "desktop_windows_ie@11": "https://storage.googleapis.com/mdc-web-screenshot-tests/travis/2019/09/10/20_51_43_383/spec/mdc-form-field/classes/baseline-radio.html.windows_ie_11.png"
-    }
-  },
   "spec/mdc-image-list/classes/standard-with-text-protection.html": {
     "public_url": "https://storage.googleapis.com/mdc-web-screenshot-tests/abhiomkar/2019/09/10/15_45_24_303/spec/mdc-image-list/classes/standard-with-text-protection.html?utm_source=golden_json",
     "screenshots": {