tests/utils/git_spec: update tests for `ensure_formula_installed!`

Library/Homebrew/test/utils/git_spec.rb

@@ -184,7 +184,7 @@ describe Utils::Git do
       unless ENV["HOMEBREW_TEST_GENERIC_OS"]
         it "installs git" do
           expect(described_class).to receive(:available?).and_return(false)
-          expect(described_class).to receive(:safe_system).with(HOMEBREW_BREW_FILE, "install", "git").and_return(true)
+          expect(described_class).to receive(:ensure_formula_installed!).with("git")
           expect(described_class).to receive(:available?).and_return(true)
 
           described_class.ensure_installed!

Library/Homebrew/utils/git.rb

@@ -94,8 +94,6 @@ module Utils
       # we cannot install brewed git if homebrew/core is unavailable.
       if CoreTap.instance.installed?
         begin
-          oh1 "Installing #{Formatter.identifier("git")}"
-
           # Otherwise `git` will be installed from source in tests that need it. This is slow
           # and will also likely fail due to `OS::Linux` and `OS::Mac` being undefined.
           raise "Refusing to install Git on a generic OS." if ENV["HOMEBREW_TEST_GENERIC_OS"]