Fix typings for ReactNativeVersion.js

This is an eager cherry pick of facebook#39784 for `0.73-stable`.

Author: huntie

Diff for: packages/react-native/Libraries/Core/ReactNativeVersionCheck.js

@@ -44,7 +44,6 @@ function _formatVersion(
 ): string {
   return (
     `${version.major}.${version.minor}.${version.patch}` +
-    // eslint-disable-next-line eqeqeq
-    (version.prerelease != undefined ? `-${version.prerelease}` : '')
+    (version.prerelease != null ? `-${version.prerelease}` : '')
   );
 }

Diff for: packages/react-native/Libraries/Utilities/NativePlatformConstantsAndroid.js

@@ -16,7 +16,7 @@ export type ReactNativeVersionAndroid = {|
   major: number,
   minor: number,
   patch: number,
-  prerelease: ?number,
+  prerelease: ?string,
 |};
 
 export type PlatformConstantsAndroid = {|

Diff for: packages/react-native/Libraries/Utilities/NativePlatformConstantsIOS.js

@@ -19,7 +19,7 @@ export type PlatformConstantsIOS = {|
     major: number,
     minor: number,
     patch: number,
-    prerelease: ?number,
+    prerelease: ?string,
   |},
   forceTouchAvailable: boolean,
   osVersion: string,

Diff for: packages/react-native/Libraries/Utilities/Platform.android.js

@@ -31,7 +31,7 @@ const Platform: PlatformType = {
       major: number,
       minor: number,
       patch: number,
-      prerelease: ?number,
+      prerelease: ?string,
     |},
     Version: number,
     Release: string,

Diff for: packages/react-native/Libraries/Utilities/Platform.flow.js

@@ -32,7 +32,7 @@ type IOSPlatform = {
       major: number,
       minor: number,
       patch: number,
-      prerelease: ?number,
+      prerelease: ?string,
     |},
     systemName: string,
   |},
@@ -60,7 +60,7 @@ type AndroidPlatform = {
       major: number,
       minor: number,
       patch: number,
-      prerelease: ?number,
+      prerelease: ?string,
     |},
     Version: number,
     Release: string,

Diff for: packages/react-native/Libraries/Utilities/Platform.ios.js

@@ -34,7 +34,7 @@ const Platform: PlatformType = {
       major: number,
       minor: number,
       patch: number,
-      prerelease: ?number,
+      prerelease: ?string,
     |},
     systemName: string,
   |} {