ci: install meson via apt instead of pip (PEP 668 / Ubuntu 24.04)

ubuntu-latest now resolves to Ubuntu 24.04 which ships meson 1.3.2 (satisfies
>=1.3.0) and enforces PEP 668, blocking pip3 install without --break-system-packages.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/test.yml

@@ -20,10 +20,9 @@ jobs:
             gstreamer1.0-plugins-good \
             libpam0g-dev \
             ninja-build \
-            python3-pip \
+            meson \
             libglib2.0-dev \
             xvfb
-          pip3 install meson
 
       - name: Install Rust stable
         uses: dtolnay/rust-toolchain@stable