Fix unused parameter warning in ExtractUncompressedSize

[namsic]

• Fix Build fails without Snappy #14309

Problem

When SNAPPY is not defined, ExtractUncompressedSize in BuiltinDecompressorV2SnappyOnly does not use the args parameter, causing a -Werror=unused-parameter compilation error:

  CC       util/compression.o
util/compression.cc: In member function ‘virtual rocksdb::Status rocksdb::{anonymous}::BuiltinDecompressorV2SnappyOnly::ExtractUncompressedSize(rocksdb::Decompressor::Args&)’:
util/compression.cc:1541:40: error: unused parameter ‘args’ [-Werror=unused-parameter]
 1541 |   Status ExtractUncompressedSize(Args& args) override {
      |                                  ~~~~~~^~~~
cc1plus: all warnings being treated as errors
make: *** [Makefile:2590: util/compression.o] Error 1

Fix

Add [[maybe_unused]] to the args parameter to suppress the warning when SNAPPY is not defined.