Set explicit types in I18nManager exports

Summary:
Changelog:
[Internal] - Added explicit types in I18nManager exports

Reviewed By: elicwhite

Differential Revision: D68214193

fbshipit-source-id: 960ef7b9c0171aed983f4db620bb895ccbff6cd2

packages/react-native/Libraries/ReactNative/I18nManager.js

@@ -56,6 +56,7 @@ module.exports = {
     NativeI18nManager.swapLeftAndRightInRTL(flipStyles);
   },
 
-  isRTL: i18nConstants.isRTL,
-  doLeftAndRightSwapInRTL: i18nConstants.doLeftAndRightSwapInRTL,
+  isRTL: i18nConstants.isRTL as I18nManagerConstants['isRTL'],
+  doLeftAndRightSwapInRTL:
+    i18nConstants.doLeftAndRightSwapInRTL as I18nManagerConstants['doLeftAndRightSwapInRTL'],
 };

packages/react-native/Libraries/__tests__/__snapshots__/public-api-test.js.snap

@@ -7489,8 +7489,8 @@ exports[`public API should not change unintentionally Libraries/ReactNative/I18n
   allowRTL: (shouldAllow: boolean) => void,
   forceRTL: (shouldForce: boolean) => void,
   swapLeftAndRightInRTL: (flipStyles: boolean) => void,
-  isRTL: $FlowFixMe,
-  doLeftAndRightSwapInRTL: $FlowFixMe,
+  isRTL: I18nManagerConstants[\\"isRTL\\"],
+  doLeftAndRightSwapInRTL: I18nManagerConstants[\\"doLeftAndRightSwapInRTL\\"],
 };
 "
 `;