Remove pipenv install from Makefile

[smaye81]

This removes the install of pipenv from the Makefile. Instead, mandating that users should install it on their own system-wide.

In addition , it fixes the pyproject.toml to use the new metadata for license-expression and license-file.

[smaye81]

We decided to remove re2 for now because there are no built wheels for Python 3.13 for some reason (issue). Will reassess in the future.

[stefanvanburen]

@smaye81 did we have a reason for pinning to this version? Wasn't sure if we needed this for something or if newer types-protobuf versions were borked in some way.

I'm guessing it's because unpinning results in:

$ make lint
pipenv --python python3 sync --dev
Loading .env environment variables...
To activate this project's virtualenv, run pipenv shell.
Alternatively, run a command inside the virtualenv with pipenv run.
Installing dependencies from Pipfile.lock (8a53a8)...
Installing dependencies from Pipfile.lock (8a53a8)...
All dependencies are now up-to-date!
pipenv run ruff format --check --diff protovalidate tests
Loading .env environment variables...
16 files already formatted
pipenv run mypy protovalidate
Loading .env environment variables...
protovalidate/internal/rules.py:69: error: Incompatible types in assignment (expression has type "google.protobuf.descriptor.Descriptor | google._upb._message.Descriptor", variable has type "google.protobuf.descriptor.Descriptor")  [assignment]
protovalidate/validator.py:88: error: Argument 1 to "get" of "RuleFactory" has incompatible type "google.protobuf.descriptor.Descriptor | google._upb._message.Descriptor"; expected "google.protobuf.descriptor.Descriptor"  [arg-type]
Found 2 errors in 2 files (checked 9 source files)
make: *** [lint] Error 1

for when we want context in the future.

[smaye81]

Yep, that's why it's pinned. For some reason, that version is out of sync with the protobuf library and expects descriptors to be a union type.