dSYM upload docs still point to deprecated method

[tmm1]

https://github.com/getsentry/sentry-docs/blob/master/src/collections/_documentation/clients/cocoa/dsym.md

mentions upload_symbols_to_sentry which is deprecated

instead it should tell users how to install fastlane-plugin-sentry and use sentry_upload_dsym

[github-actions]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you label it Status: Accepted, I will leave it alone ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀