Fix PEP 668 externally-managed-environment error on macOS

Add --user flag to all pip install commands on macOS to comply with
PEP 668 restrictions in Python 3.12+. This installs sympy to the
user directory instead of system-wide, which is allowed and safe.

Author: ahmed-irfan

.github/actions/install-dependencies/action.yml

@@ -25,11 +25,11 @@ runs:
         # brew install gmp
         # brew install python
         if command -v pip3 &> /dev/null; then
-          pip3 install sympy
+          pip3 install --user sympy
         elif python3 -m pip --version &> /dev/null; then
-          python3 -m pip install sympy
+          python3 -m pip install --user sympy
         else
           python3 -m ensurepip --upgrade || python3 -m ensurepip
-          python3 -m pip install sympy
+          python3 -m pip install --user sympy
         fi
         echo "Install Mac dependencies [DONE]"