fix(python): Remove memcached references (#15380)

Remove indications that `memcached` support is coming soon in the Python SDK.

Support for `memcached` is currently not priority, and therefore not
coming soon. See the issue getsentry/sentry-python#2966

Author: alexander-alderman-webb

docs/platforms/python/tracing/instrumentation/custom-instrumentation/caches-module.mdx

@@ -5,7 +5,7 @@ description: "Learn how to manually instrument your code to use Sentry's Caches
 ---
 A cache can be used to speed up data retrieval, thereby improving application performance. Because instead of getting data from a potentially slow data layer, your application will be getting data from memory (in a best case scenario). Caching can speed up read-heavy workloads for applications like Q&A portals, gaming, media sharing, and social networking.
 
-Sentry offers a [cache-monitoring dashboard](https://sentry.io/orgredirect/organizations/:orgslug/insights/backend/caches/) that can be auto-instrumented for popular Python caching setups (like <PlatformLink to="/integrations/django/">Django</PlatformLink>, <PlatformLink to="/integrations/redis/">Redis</PlatformLink>, and memcached (coming soon)).
+Sentry offers a [cache-monitoring dashboard](https://sentry.io/orgredirect/organizations/:orgslug/insights/backend/caches/) that can be auto-instrumented for popular Python caching setups (like <PlatformLink to="/integrations/django/">Django</PlatformLink> and <PlatformLink to="/integrations/redis/">Redis</PlatformLink>).
 
 If you're using a custom caching solution that doesn't have auto instrumentation, you can manually instrument it and use Sentry to get a look into how your caching solution is performing by following the setup instructions below.
 
@@ -17,7 +17,7 @@ For detailed information about which data can be set, see the [Cache Module Deve
 
 ## Manual Instrumentation
 
-If you're using anything other than <PlatformLink to="/integrations/django/">Django</PlatformLink>, <PlatformLink to="/integrations/redis/">Redis</PlatformLink>,  memcached (coming soon), you'll need to manually instrument the [Cache Module](https://sentry.io/orgredirect/organizations/:orgslug/insights/backend/caches/) by following the steps below.
+If you're using anything other than <PlatformLink to="/integrations/django/">Django</PlatformLink> or <PlatformLink to="/integrations/redis/">Redis</PlatformLink>, you'll need to manually instrument the [Cache Module](https://sentry.io/orgredirect/organizations/:orgslug/insights/backend/caches/) by following the steps below.
 
 ### Add Span When Putting Data Into the Cache