## Description 
Fix testnet compatibility check

## Test Plan 
```
eugene@eugene-dev ~/code/sui/ (ebmifa/fix_compatibility_check_for_testnet) $ ./scripts/compatibility/check-protocol-compatibility.sh testnet
Found following versions on testnet:
     45 1.21.0-10da1ccdde8b
     20 1.20.0-8ea60086a548
     15 1.21.0-10da1ccdde
     11 1.20.0-8ea60086a5
      1 1.20.1-cdd6903310
      1 1.20.0-04c9b08b6326

Using most frequent version 1.21.0-10da1ccdde8b for compatibility check
Checking protocol compatibility with testnet (10da1ccdde8b)
Checking out testnet snapshot files
Checking for changes to snapshot files matching *__Testnet_version_*
HEAD is now at 9b79090c28 add testnet clause
Running snapshot tests...
    Finished test [unoptimized + debuginfo] target(s) in 0.28s
     Running unittests src/lib.rs (target/debug/deps/sui_protocol_config-9081412e1cdb3455)

running 1 test
test test::snapshot_tests ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 4 filtered out; finished in 0.33s
```