Remove babel plugins from jest preprocessor which are part of preset

Summary:
Changelog:
[Internal][Changed] - Remove babel plugins from jest preprocessor which are part of preset metro-react-native-babel-preset

Transformer metro-react-native-babel-transformer has preset metro-react-native-babel-preset which has necessary plugins to transpile the source. So we don’t need to pass it again in the preprocessor.

As part of the change, updated one test to use strict mode since metro-react-native-babel-preset has strictMode is set to false.

Reviewed By: motiz88

Differential Revision: D34868961

fbshipit-source-id: 71678f1ee6f1b5ebf9a0c6fd2d6444a61d7583ac

Libraries/Network/__tests__/XMLHttpRequest-test.js

@@ -8,6 +8,8 @@
  * @emails oncall+react_native
  */
 
+'use strict';
+
 import createPerformanceLogger from '../../Utilities/createPerformanceLogger';
 
 jest.unmock('../../Utilities/Platform');

jest/private/preprocessor.js

@@ -59,43 +59,6 @@ module.exports = {
         sourceType: 'unambiguous', // b7 required. detects module vs script mode
       },
       src,
-      plugins: [
-        [require('@babel/plugin-transform-block-scoping')],
-        // the flow strip types plugin must go BEFORE class properties!
-        // there'll be a test case that fails if you don't.
-        [require('@babel/plugin-transform-flow-strip-types')],
-        [
-          require('@babel/plugin-proposal-class-properties'),
-          // use `this.foo = bar` instead of `this.defineProperty('foo', ...)`
-          {loose: true},
-        ],
-        [require('@babel/plugin-transform-computed-properties')],
-        [require('@babel/plugin-transform-destructuring')],
-        [require('@babel/plugin-transform-function-name')],
-        [require('@babel/plugin-transform-literals')],
-        [require('@babel/plugin-transform-parameters')],
-        [require('@babel/plugin-transform-shorthand-properties')],
-        [require('@babel/plugin-transform-react-jsx')],
-        [require('@babel/plugin-transform-regenerator')],
-        [require('@babel/plugin-transform-sticky-regex')],
-        [require('@babel/plugin-transform-unicode-regex')],
-        [
-          require('@babel/plugin-transform-modules-commonjs'),
-          {strict: false, allowTopLevelThis: true},
-        ],
-        [require('@babel/plugin-transform-classes')],
-        [require('@babel/plugin-transform-arrow-functions')],
-        [require('@babel/plugin-transform-spread')],
-        [require('@babel/plugin-proposal-object-rest-spread')],
-        [
-          require('@babel/plugin-transform-template-literals'),
-          {loose: true}, // dont 'a'.concat('b'), just use 'a'+'b'
-        ],
-        [require('@babel/plugin-transform-exponentiation-operator')],
-        [require('@babel/plugin-transform-for-of'), {loose: true}],
-        [require('@babel/plugin-transform-react-display-name')],
-        [require('@babel/plugin-transform-react-jsx-source')],
-      ],
     });
 
     return generate(