chore: fix semantic-release build_command to use python -m build

PSR's action environment does not have uv available, so uv build fails.
Switch to python -m build (installing it via pip) and remove the now-
unnecessary setup-uv step from release.yml.

Ref: openedx/XBlock#928

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: salman2013

.github/workflows/release.yml

@@ -36,9 +36,6 @@ jobs:
         with:
           python-version: "3.12"
 
-      - name: Install uv
-        uses: astral-sh/setup-uv@v6
-
       - name: Set up Node.js
         uses: actions/setup-node@v6
         with:

pyproject.toml

@@ -185,4 +185,4 @@ constraint-dependencies = [
 [tool.semantic_release]
 # We use SETUPTOOLS_SCM_PRETEND_VERSION to pull the version from python-semantic-release
 # instead of from version control because the build step happens before the repo gets tagged.
-build_command = "SETUPTOOLS_SCM_PRETEND_VERSION=$NEW_VERSION uv build"
+build_command = "python -m pip install --upgrade build && SETUPTOOLS_SCM_PRETEND_VERSION=$NEW_VERSION python -m build"