Docs: Update install guides link in README (#56116)

This updates the link to the installation guides in the README to the docs for the latest Grafana version, whereas the previous redirect was going to v9.0. This also improves the security of the link, which was previously insecure http://.

README.md

@@ -18,7 +18,7 @@ Grafana allows you to query, visualize, alert on and understand your metrics no
 ## Get started
 
 - [Get Grafana](https://grafana.com/get)
-- [Installation guides](http://docs.grafana.org/installation/)
+- [Installation guides](https://grafana.com/docs/grafana/latest/setup-grafana/installation/)
 
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