benchmark openh264_decoder_fuzzer corpus URL outdated

It seems like the corpus URL in the openh264_decoder_fuzzer benchmark is invalid and outdated.

outdated URL: `https://github.com/mozillasecurity/fuzzdata.git/trunk/samples/h264`

Could you update this, please?

```
53.55 [build 0/2] build target binary
55.48 Building benchmark openh264_decoder_fuzzer with fuzzer aflplusplus
55.48 + svn export https://github.com/mozillasecurity/fuzzdata.git/trunk/samples/h264 corpus/
55.52 svn: E170013: Unable to connect to a repository at URL 'https://github.com/mozillasecurity/fuzzdata.git/trunk/samples/h264'
55.52 svn: E215004: No more credentials or we tried too many times.
55.52 Authentication failed
55.59 Traceback (most recent call last):
55.59 File "", line 1, in
55.59 File "/src/fuzzers/aflplusplus/fuzzer.py", line 80, in build
55.59 utils.build_benchmark()
55.59 File "/src/fuzzers/utils.py", line 81, in build_benchmark
55.59 subprocess.check_call(['/bin/bash', '-ex', build_script], env=env)
55.59 File "/usr/local/lib/python3.10/subprocess.py", line 369, in check_call
55.59 raise CalledProcessError(retcode, cmd)
55.59 subprocess.CalledProcessError: Command '['/bin/bash', '-ex', '/src/build.sh']' returned non-zero exit status 1.
```