docs(site): update homebrew installation instructions
Since we now have official kopia formula in the `homebrew-core` repo,
dedicated `kopia` TAP is no longer needed (we will keep publishing to
it for a while so it's available as a fallback).
Fixes
@@ -74,7 +74,7 @@ On macOS, you can use [Homebrew](https://brew.sh) to install and keep Kopia up-t
To install:
```shell
-$ brew install kopia/kopia/kopia
+$ brew install kopia
```
To upgrade Kopia:
