Use official Homebrew formula

vladimyr · Stephan Dilly · commit 35926efe5ec7 · 2020-06-16T21:33:45.000+02:00
diff --git a/README.md b/README.md
@@ -91,7 +91,7 @@ sudo dnf install gitui
 ## homebrew (macos)
 
 ```
-brew install extrawurst/tap/gitui
+brew install gitui
 ```
 
 ## release binaries
