cifuzz: use the default runtime of 600 seconds

The default runtime for CIFuzz[1] is 600 seconds; use it.

Since GitHub pull-requests are not the main contribution workflow the
number of runs should be manageable.

[1]: https://google.github.io/oss-fuzz/getting-started/continuous-integration/

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>

.github/workflows/cifuzz.yml

@@ -28,7 +28,7 @@ jobs:
         uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
         with:
           oss-fuzz-project-name: 'selinux'
-          fuzz-seconds: 180
+          fuzz-seconds: 600
           dry-run: false
           report-unreproducible-crashes: true
           sanitizer: ${{ matrix.sanitizer }}