Using outdated cached fuzzer repo.

# Problem
FuzzBench uses a cached fuzzer repo instead of the latest one, which sometimes does not include the new commits required.

# Proof of Error
https://github.com/google/fuzzbench/pull/1902#issuecomment-1737463393

# Proposed solution
Removing [this](https://github.com/google/fuzzbench/blob/7c70037a73d2cc66627c6109d53d20b3594f85c9/docker/generate_makefile.py#L123-L124).

@jonathanmetzman Would this look good to you?
Those two lines originated from [here](https://github.com/google/fuzzbench/pull/388/files#diff-9ba00a2744edb4b6e8a4768b520cd4b147e26ddec73c13337aac6a79ccfa99a0R33).
Please let me know if I missed anything (e.g., side-effects of removing them, other preferred solutions), thanks : )