CI Linux: lining it up with the other workflow yml files and don't in…

…stall tkinter_gl from source.

.github/workflows/linux.yml

@@ -30,8 +30,7 @@ jobs:
             pip install --pre --extra-index-url https://test.pypi.org/simple cypari &&
             pip install git+https://github.com/3-manifolds/PLink &&
             pip install git+https://github.com/3-manifolds/snappy_manifolds &&
-            pip install git+https://github.com/3-manifolds/Spherogram &&
-            pip install git+https://github.com/3-manifolds/tkinter_gl
+            pip install git+https://github.com/3-manifolds/Spherogram
           CIBW_REPAIR_WHEEL_COMMAND_LINUX: auditwheel repair --strip -w {dest_dir} {wheel}
           CIBW_TEST_COMMAND: python -m snappy.test --skip-modern-opengl