fix: Removed version func from feature_store.py

[dandawg]

What this PR does / why we need it:

This PR removes the version function from feature_store.py, which is a method to the FeatureStore class. The version method was unused, un-needed, and confusing. See issue #4747 for more details.

I categorized this as a "fix" because I see an unused/un-needed function as a bug, but I understand that this could merit a different categorization.

Which issue(s) this PR fixes:

4747

[dandawg]

I used vscode's 'references' functionality to verify that this function was unused in the repo. To double check this, I also did the following:

# search for all mentions of version(
# excluding ones like ..._version(, ...conversion(, etc.
# also excludes lines with venv (my virtual env files)
grep -R '[^A-z_]version(' . | grep -v "venv" 

Output:

./sdk/python/feast/feature_store.py:    def version(self) -> str:
./sdk/python/feast/version.py:        sdk_version = version("feast")
./sdk/python/feast/cli.py:def version():
./build/lib/feast/feature_store.py:    def version(self) -> str:
./build/lib/feast/version.py:        sdk_version = version("feast")
./build/lib/feast/cli.py:def version():

I manually verified that ./sdk/python/feast/version.py and ./build/lib/feast/version.py are not using feature_store.FeatureStore.version.