docs: update installation guide with corrected links for language models and PR-Agent Pro details

Author: mrT23

docs/docs/installation/index.md

@@ -3,7 +3,7 @@
 ## Self-hosted PR-Agent
 If you choose to host you own PR-Agent, you first need to acquire two tokens:
 
-1. An OpenAI key from [here](https://platform.openai.com/api-keys), with access to GPT-4 (or a key for [other models](../usage-guide/additional_configurations.md/#changing-a-model), if you prefer).
+1. An OpenAI key from [here](https://platform.openai.com/api-keys), with access to GPT-4 (or a key for other [language models](https://pr-agent-docs.codium.ai/usage-guide/changing_a_model/), if you prefer).
 2. A GitHub\GitLab\BitBucket personal access token (classic), with the repo scope. [GitHub from [here](https://github.com/settings/tokens)]
 
 There are several ways to use self-hosted PR-Agent:
@@ -18,4 +18,4 @@ There are several ways to use self-hosted PR-Agent:
 PR-Agent Pro, an app hosted by CodiumAI for GitHub\GitLab\BitBucket, is also available. 
 <br>
 With PR-Agent Pro, installation is as simple as signing up and adding the PR-Agent app to your relevant repo. 
-See [here](./pr_agent_pro.md) for more details.
+See [here](https://pr-agent-docs.codium.ai/installation/pr_agent_pro/) for more details.