rn: raise SDK version to 2.8.1

android/gradle.properties

 android.enableJetifier=true
 
 appVersion=20.3.0
-sdkVersion=2.8.0
+sdkVersion=2.8.1

ios/sdk/src/Info.plist

 	<key>CFBundlePackageType</key>
 	<string>FMWK</string>
 	<key>CFBundleShortVersionString</key>
-	<string>2.8.0</string>
+	<string>2.8.1</string>
 	<key>CFBundleVersion</key>
 	<string>$(CURRENT_PROJECT_VERSION)</string>
 	<key>NSPrincipalClass</key>