Update dependency uv to v0.5.21 (#282)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

charmcraft.yaml

@@ -27,7 +27,7 @@ parts:
       PIP_BREAK_SYSTEM_PACKAGES=true python3 -m pip install --user --upgrade pip==24.3.1  # renovate: charmcraft-pip-latest
 
       # Use uv to install poetry so that a newer version of Python can be installed if needed by poetry
-      curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/uv/releases/download/0.5.20/uv-installer.sh | sh  # renovate: charmcraft-uv-latest
+      curl --proto '=https' --tlsv1.2 -LsSf https://github.com/astral-sh/uv/releases/download/0.5.21/uv-installer.sh | sh  # renovate: charmcraft-uv-latest
       # poetry 2.0.0 requires Python >=3.9
       if ! "$HOME/.local/bin/uv" python find '>=3.9'
       then