Swap `should_run_glt_backend` feature flag to default true.

[kmontemayor2-sc]

Per https://github.com/Snapchat/GiGL/pull/433/files#r2700472800 we should update

GiGL/python/gigl/src/common/types/pb_wrappers/gbml_config.py

Line 462 in 9bb5d85

"should_run_glt_backend", "False"

to default to true.

Let's make sure there's no usage of this other behavior first :)