gradle-completion: don't depend on bash-completion (#91042)

A formula that `depends_on "bash-completion"` cannot be installed on a
system that has `bash-completion@2` installed without errors, unless
using `--ignore-dependencies` which is not ideal when automating via
e.g. ansible.

For reference, both [maven-completion][1] and [rustc-completion][2] do
not have `depends_on "bash-completion"` in their formulae.

[1]: https://github.com/Homebrew/homebrew-core/blob/master/Formula/maven-completion.rb
[2]: https://github.com/Homebrew/homebrew-core/blob/master/Formula/rustc-completion.rb

Formula/gradle-completion.rb

@@ -10,8 +10,6 @@ class GradleCompletion < Formula
     sha256 cellar: :any_skip_relocation, all: "6889d645ade2d3296031a3bdebaec9c2622bf26755fae51024e1692f6872ccb3"
   end
 
-  depends_on "bash-completion"
-
   def install
     bash_completion.install "gradle-completion.bash" => "gradle"
     zsh_completion.install "_gradle" => "_gradle"