docs: standardize the Homebrew install command

The install docs used different Homebrew commands in different places.
Update the user-facing docs to use the confirmed cask command everywhere
so the install path is consistent.

Author: chmouel

README.md

@@ -77,7 +77,7 @@ Full documentation is at **<https://pipelinesascode.com>**
 Install the CLI and bootstrap your first repository:
 
 ```shell
-brew install tektoncd/pipelines-as-code/tkn-pac
+brew install --cask openshift-pipelines/pipelines-as-code/tektoncd-pac
 tkn pac bootstrap
 ```
 

docs/content/docs/cli/installation.md

@@ -27,7 +27,7 @@ On Windows, tkn-pac will look for the Kubernetes config in `%USERPROFILE%\.kube\
 {{< /tab >}}
 
 {{< tab name="Homebrew" >}}
-The `tkn pac` plug-in is available from Homebrew as a "Tap". Install it with:
+The `tkn pac` plug-in is available from Homebrew as a cask. Install it with:
 
 ```shell
 brew install --cask openshift-pipelines/pipelines-as-code/tektoncd-pac

docs/content/docs/installation/requirements.md

@@ -104,7 +104,7 @@ The Pipelines-as-Code CLI plugin for `tkn`.
 **Install via Homebrew**:
 
 ```bash
-brew install openshift-pipelines/pipelines-as-code/tkn-pac
+brew install --cask openshift-pipelines/pipelines-as-code/tektoncd-pac
 ```
 
 **Install via Direct Download** (Linux):