ref(js): change migration guide URLs from v7 branch to master (#5087)

This small PR changes the URLs of two links to the JS SDK migration guide which previously linked to the 7.x branch version of the migration guide. It now links to master since we merged the 7.x branch

Author: Lms24

src/includes/getting-started-install/javascript.mdx

@@ -11,5 +11,4 @@ We also support alternate [installation methods](/platforms/javascript/install/)
 
 </Note>
 
- If you're updating your Sentry SDK to the latest version, check out our [migration guide](https://github.com/getsentry/sentry-javascript/blob/7.x/MIGRATION.md) to learn more about breaking changes.
-
+If you're updating your Sentry SDK to the latest version, check out our [migration guide](https://github.com/getsentry/sentry-javascript/blob/master/MIGRATION.md) to learn more about breaking changes.

src/platforms/javascript/common/troubleshooting/index.mdx

@@ -12,7 +12,7 @@ If you need help solving issues with your Sentry JavaScript SDK integration, you
 ## Updating to a New Sentry SDK Version
 
 If you update your Sentry SDK to a new major version, you might encounter breaking changes that need some adaption on your end.
-Check out our [migration guide](https://github.com/getsentry/sentry-javascript/blob/7.x/MIGRATION.md) to learn everything you need
+Check out our [migration guide](https://github.com/getsentry/sentry-javascript/blob/master/MIGRATION.md) to learn everything you need
 to know to get up and running again with the latest Sentry features.
 
 ## Debugging Additional Data