[CI] Increase timeout in check-first-frame-is-sid

The job https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/jobs/282706 failed on Ericsson sprinter1 due to timeout. The test samples are 20 seconds long and the 10 second timeout should be sufficient. However, the timeouts appear even if no other jobs were running on the computer. One guess is that the file access becomes a bottleneck -- the failing cases were ISM4 encoding, which have several input files.

This MR just increases the timeout on the test cases to 20 seconds, which seems to solve the issue on sprinter1 when testing locally.