Fixed RCTAssert nullability

Summary:
```
Apps/Instagram/AppLibraries/IGReactKit/IGReactKit/IGReactRouteHelpers.m:54:5: error: implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull' [-Werror,-Wnullable-to-nonnull-conversion]
    RCTAssert(!(title != nil && logoAsTitle), @"Screen navigationOptions cannot have both title and logoAsTitle.");
    ^
Apps/Instagram/AppLibraries/IGReactKit/IGReactKit/IGReactRouteHelpers.m:54:5: error: implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull' [-Werror,-Wnullable-to-nonnull-conversion]
/data/sandcastle/boxes/trunk-hg-fbobjc-fbsource/xplat/js/react-native-github/React/Base/RCTAssert.h:28:14: note: expanded from macro 'RCTAssert'
        file:@(__FILE__) lineNumber:__LINE__ description:__VA_ARGS__]; \

```

Reviewed By: zats

Differential Revision: D8509133

fbshipit-source-id: ae7027efc18716193c86fbeeec74d41d1879797f

Author: dinhvh

React/Base/RCTAssert.h

@@ -25,7 +25,7 @@ RCT_EXTERN BOOL RCTIsMainQueue(void);
     _RCTAssertFormat(#condition, __FILE__, __LINE__, __func__, __VA_ARGS__); \
     if (RCT_NSASSERT) { \
       [[NSAssertionHandler currentHandler] handleFailureInFunction:@(__func__) \
-        file:@(__FILE__) lineNumber:__LINE__ description:__VA_ARGS__]; \
+        file:(NSString * _Nonnull)@(__FILE__) lineNumber:__LINE__ description:__VA_ARGS__]; \
     } \
   } \
 } while (false)