Unpin the pip version in setupVirtualenv (#36745)

* Unpin the pip version in setupVirtualenv

* trigger a python precommit to test

Author: jrmccluskey

.github/trigger_files/beam_PreCommit_Python_ML.json

@@ -0,0 +1,4 @@
+{
+  "comment": "Modify this file in a trivial way to cause this test suite to run.",
+  "modification": 0
+}

buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy

@@ -3122,12 +3122,8 @@ class BeamModulePlugin implements Plugin<Project> {
           }
           project.exec {
             executable 'sh'
-            // TODO: https://github.com/apache/beam/issues/29022
-            // pip 23.3 is failing due to Hash mismatch between expected SHA of the packaged and actual SHA.
-            // until it is resolved on pip's side, don't use pip's cache.
-            // pip 25.1 casues :sdks:python:installGcpTest stuck. Pin to 25.0.1 for now.
             args '-c', ". ${project.ext.envdir}/bin/activate && " +
-                "pip install --pre --retries 10 --upgrade pip==25.0.1 --no-cache-dir && " +
+                "pip install --pre --retries 10 --upgrade pip --no-cache-dir && " +
                 "pip install --pre --retries 10 --upgrade tox --no-cache-dir"
           }
         }