Use --upgrade-strategy=eager for pip

Author: AA-Turner

build_docs.py

@@ -790,6 +790,7 @@ def build_venv(self):
         run([sys.executable, "-m", "venv", venv_path])
         run(
             [venv_path / "bin" / "python", "-m", "pip", "install", "--upgrade"]
+            + ["--upgrade-strategy=eager"]
             + [self.theme]
             + self.version.requirements,
             cwd=self.checkout / "Doc",