Only show Browser vs React Native source maps alert for browser sdks (#12816)

Co-authored-by: Luca Forstner <[email protected]>

Author: krystofwoldrich

platform-includes/sourcemaps/overview/javascript.mdx

@@ -4,12 +4,16 @@ The easiest way to configure uploading source maps is by using the Sentry Wizard
 
 <Include name="sourcemaps-wizard-instructions.mdx" />
 
+<PlatformSection supported={['javascript', 'javascript.react']}>
+
 <Alert>
 
 This guide assumes you are using a Browser JavaScript SDK. For instructions on how to set up source maps for React Native, follow the [source maps guide for React Native](/platforms/react-native/sourcemaps/).
 
 </Alert>
 
+</PlatformSection>
+
 If you want to configure source maps upload manually, follow the guide for your bundler or build tool below.
 
 <PlatformSection supported={["javascript.react"]}>