Update the version of gbenchmark

[TotoGaz]

Hello,

When using BLT we use the embedded google benchmark which is currently at version 1.5.0.
With recent compilers (e.g. clang13, and I've been told gcc12), we face some "unused variable error" (google/benchmark#1172)

/Users/travis/build/GEOSX/GEOSX/src/cmake/blt/thirdparty_builtin/benchmark-1.5.0/src/complexity.cc:85:10: error: variable 'sigma_gn' set but not used [-Werror,-Wunused-but-set-variable]
  double sigma_gn = 0.0;

which was fixed in the latest release of google benchmark 1.7.0 (google/benchmark#1174) see https://github.com/google/benchmark/blob/v1.7.0/src/complexity.cc

Could you upgrade such that we're able to build seamlessly?

Thx!

[white238]

Fixed in #627