Refactor xcodeproj FB_SONARKIT_ENABLED flag to macro

Should have been added as an Apple Clang preprocessor macro (not compiler flag) in our RN 0.62.2 upg:
#1586

Refactor in xcodeproj target
- from: Apple Clang - Custom Compiler Flags > Other C Flags
- to: Apple Clang - Preprocessing > Preprocessor Macros

Ref: https://github.com/facebook/react-native/blob/v0.62.0/template/ios/HelloWorld.xcodeproj/project.pbxproj#L500

Nb: rn-tester sticking to "-DFB_SONARKIT_ENABLED=1" for OTHER_CFLAGS and OTHER_SWIFT_FLAGS

ios/MetaMask.xcodeproj/project.pbxproj

@@ -1016,6 +1016,7 @@
 				GCC_PREPROCESSOR_DEFINITIONS = (
 					"DEBUG=1",
 					"$(inherited)",
+					"FB_SONARKIT_ENABLED=1",
 				);
 				HEADER_SEARCH_PATHS = (
 					"$(inherited)",
@@ -1038,10 +1039,7 @@
 				LLVM_LTO = YES;
 				MARKETING_VERSION = 7.8.0;
 				ONLY_ACTIVE_ARCH = YES;
-				OTHER_CFLAGS = (
-					"$(inherited)",
-					"-DFB_SONARKIT_ENABLED=1",
-				);
+				OTHER_CFLAGS = "$(inherited)";
 				OTHER_LDFLAGS = (
 					"$(inherited)",
 					"-ObjC",