git-gui: use tcl-tk@8

Author: surjikal

Formula/git-gui.rb

@@ -14,7 +14,7 @@ class GitGui < Formula
     sha256 cellar: :any_skip_relocation, all: "f81fbb5712226c0bc86b93df3b0907b9633ffcf571b4c94a1fd064b98e20e39e"
   end
 
-  depends_on "surjikal/tap/tcl-tk"
+  depends_on "tcl-tk@8"
 
   # Patch to fix Homebrew/homebrew-core#68798.
   # Remove when the following PR has been merged
@@ -44,7 +44,7 @@ def install
     # the git makefiles don't install a .app for git-gui
     # We also tell git to use the homebrew-installed wish binary from tcl-tk.
     # See https://github.com/Homebrew/homebrew-core/issues/36390
-    tcl_bin = Formula["tcl-tk"].opt_bin
+    tcl_bin = Formula["tcl-tk@8"].opt_bin
     args = %W[
       TKFRAMEWORK=/dev/null
       prefix=#{prefix}