ci: drop the stray version echo left in the player-perf ffmpeg step

Converting the step to the shared action left the trailing `ffmpeg -version`
line behind, and YAML folded it into the `uses:` value — so the runner looked
for an action at a path with the command appended and failed all four perf
shards.

It parsed cleanly, which is why validating with a YAML load did not catch it:
`uses: ./path\n  ffmpeg -version` is a legal folded scalar. The check that
does catch it asserts every local `uses:` resolves to a directory containing
an action file, which is now what I ran. The action prints the version itself.

Author: miguel-heygen

.github/workflows/player-perf.yml

@@ -106,7 +106,6 @@ jobs:
       - name: Install ffmpeg (parity shard only)
         if: matrix.shard == 'parity'
         uses: ./.github/actions/install-ffmpeg-linux
-          ffmpeg -version | head -n 1
 
       - name: Run player perf — ${{ matrix.shard }} (measure mode)
         working-directory: packages/player