docs: update archlinux commands (#2876)

README.md

@@ -39,6 +39,7 @@ Get Trivy by your favorite installation method. See [installation] section in th
 
 - `apt-get install trivy`
 - `yum install trivy`
+- `pacman -S trivy`
 - `brew install aquasecurity/trivy/trivy`
 - `sudo port install trivy`
 - `docker run aquasec/trivy`

docs/getting-started/installation.md

@@ -46,19 +46,11 @@
 
 ## Arch Linux
 
-Package trivy-bin can be installed from the Arch User Repository.
+Package trivy can be installed from the Arch Community Package Manager.
 
-=== "pikaur"
-
-    ``` bash
-    pikaur -Sy trivy-bin
-    ```
-
-=== "yay"
-
-    ``` bash
-    yay -Sy trivy-bin
-    ```
+```bash
+pacman -S trivy
+```
 
 ## Homebrew