test(pkg-tests): Fix duplicate module errors from pkg-tests (#5636)

**Summary**

Adds pkg-tests-fixtures to module ignore path for Jest to avoid duplicate module errors during test
runs.

**Test plan**

Run `yarn test-only --clearCache; yarn test-only` and make sure you
don't see any `duplicate @providesModule` errors from pkg-tests folder.

package.json

@@ -120,13 +120,9 @@
     "commit": "git-cz"
   },
   "jest": {
-    "collectCoverageFrom": [
-      "src/**/*.js"
-    ],
+    "collectCoverageFrom": ["src/**/*.js"],
     "testEnvironment": "node",
-    "modulePathIgnorePatterns": [
-      "__tests__/fixtures/"
-    ],
+    "modulePathIgnorePatterns": ["__tests__/fixtures/", "packages/pkg-tests/pkg-tests-fixtures"],
     "testPathIgnorePatterns": [
       "__tests__/(fixtures|__mocks__)/",
       "updates/",
@@ -139,4 +135,4 @@
       "path": "./node_modules/cz-conventional-changelog"
     }
   }
-}
+}