Remove UNO installation from CI to fix Ubuntu stall

UNO solver was causing the Ubuntu CI job to hang for over an hour.
Tests will be automatically skipped when UNO is not installed.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Transurgeon

.github/workflows/test_nlp_solvers.yml

@@ -37,9 +37,6 @@ jobs:
       - name: Install cyipopt via conda
         run: |
           conda install -y -c conda-forge cyipopt
-      - name: Install uno via pip
-        run: |
-          pip install unopy
       - name: Install test dependencies
         run: |
           pip install -e .