fix: link to options/defaults.py in documentation (#15892)

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* Updated the instructions to specify `src/sentry/options/defaults.py`
as the correct location for adding new options, instead of
`sentry/options/defaults.py`.

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Author: vaind

develop-docs/backend/application-domains/options.mdx

@@ -13,7 +13,7 @@ While the process for creating and using options in the codebase is universal, t
 
 ## Adding New Options
 
-The process for registering a new option is the same for all environments and is done in the Sentry codebase. Add your option to [`sentry/options/defaults.py`](https://github.com/getsentry/sentry/blob/master/src/sentry/options/defaults.py).
+The process for registering a new option is the same for all environments and is done in the Sentry codebase. Add your option to [`src/sentry/options/defaults.py`](https://github.com/getsentry/sentry/blob/master/src/sentry/options/defaults.py).
 
 ```python
 register("performance.some-feature-rate", default=0.0)