Upgrade to py03 0.15.1.

This includes a fix we were waiting on in pantsbuild#13526:
  PyO3/pyo3#1990

Changelog here: https://pyo3.rs/v0.15.1/changelog.html

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]

src/rust/engine/Cargo.toml

@@ -134,8 +134,7 @@ num_enum = "0.4"
 parking_lot = "0.11"
 petgraph = "0.5"
 process_execution = { path = "process_execution" }
-# TODO: Switch back to official PyO3 once https://github.com/PyO3/pyo3/pull/1990 is released.
-pyo3 = { git = "https://github.com/PyO3/pyo3.git", rev = "45059cbdb81fd3ab72a5ce530e3b99cc90383327" }
+pyo3 = "0.15.1"
 rand = "0.8"
 regex = "1"
 reqwest = { version = "0.11", default_features = false, features = ["stream", "rustls-tls"] }
@@ -162,7 +161,7 @@ fs = { path = "./fs" }
 env_logger = "0.5.4"
 
 [build-dependencies]
-pyo3-build-config = "0.15"
+pyo3-build-config = "0.15.1"
 
 [patch.crates-io]
 # TODO: Waiting for release after https://github.com/mitsuhiko/console/pull/93.