GHA/linux: add missing condition for nghttp2-filc cache step

Follow-up to 67ef4a34f2e11aa45f0965909d0dd542643deede #19457

Closes #19548
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index fd70d82..90376ac 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -439,6 +439,7 @@
           cmake --install .
 
       - name: 'cache nghttp2 (filc)'
+        if: ${{ contains(matrix.build.install_steps, 'nghttp2-filc') }}
         uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
         id: cache-nghttp2-filc
         env: