GH-46690: [GLib][CI] Use Meson 1.8.4 or later (#47425)

### Rationale for this change

Meson 1.8.3 has wrong detection logic. It breaks our CI.

See also: mesonbuild/meson#14856

### What changes are included in this PR?

Use Meson 1.8.4 or later by explicit `brew update`.

We can remove the explicit `brew update` once GitHub hosted runners include Meson 1.8.4 or later by default.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* GitHub Issue: #46690

Authored-by: Sutou Kouhei <[email protected]>
Signed-off-by: Raúl Cumplido <[email protected]>

Author: kou

.github/workflows/ruby.yml

@@ -157,11 +157,9 @@ jobs:
       - name: Install Homebrew Dependencies
         shell: bash
         run: |
-          # pkg-config formula is deprecated but it's still installed
-          # in GitHub Actions runner now. We can remove this once
-          # pkg-config formula is removed from GitHub Actions runner.
-          brew uninstall pkg-config || :
-          brew uninstall [email protected] || :
+          # We can remove this once GitHub hosted runners include
+          # Meson 1.8.4 or later by default.
+          brew update
           brew bundle --file=cpp/Brewfile
           brew bundle --file=c_glib/Brewfile
           # For Meson.