Don't hardcode assumed python3 path in .bazelrc

Instead, tell pybind11 which python version to look
out for. Internally it assembles "python" + $python_version.

The environment has python3 in the path.

If the python3 binary is at a different place than expected,
the README has a description how to override:
https://github.com/google/xls#building-from-source

PiperOrigin-RevId: 511213683

.bazelrc

@@ -1,4 +1,3 @@
-build --action_env=PYTHON_BIN_PATH=/usr/bin/python3
 build --action_env=BAZEL_CXXOPTS=-std=c++17
 build --cxxopt "-std=c++17"
 build --copt "-Wno-sign-compare"

WORKSPACE

@@ -51,7 +51,7 @@ load_external_repositories()
 # We have to configure Python before gRPC tries to configure it a different
 # way.
 load("@pybind11_bazel//:python_configure.bzl", "python_configure")
-python_configure(name = "local_config_python")
+python_configure(name = "local_config_python", python_version="3")
 
 # gRPC deps should be loaded before initializing other repos. Otherwise, various
 # errors occur during repo loading and initialization.