tests: internal: fuzzer: limit input size
tests: internal: fuzzer: limit input size

Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=35730

The issue is not really interesting, but is just a consequence of
processing large amounts of data which is to be expected.

Signed-off-by: David Korczynski <aa743a0aaec8f7d7a1f01442503957f4d7a2d634@adalogics.com>

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