Fix pip uninstall command in qiskit-neko (#11826)

The pip uninstall command used in the qiskit neko job was missing the -y
flag used to force pip to run the uninstall. Instead it was failing on
the prompt to confirm the uninstall and then not uninstalling an
existing install because of the failure. This has been causing us to not
actually test the propsed PR because it was mixing the state of qiskit <
1.0 from pypi and >=1.0. Now that 1.0 has been released we're hitting
failures in CI because all the breaking API changes we introduced in 1.0
are finally being run and the test suite is and downstream packages we
were integration testing with are now broken. This commit fixes the
uninstall command (although arguably it probably could be removed). The
neko job will still fail with this applied as we'll need to fix it
upstream but this is currently blocked on a qiskit-nature release.

(cherry picked from commit 12f24a7)

.github/workflows/neko.yml

@@ -16,4 +16,6 @@ jobs:
       - uses: Qiskit/qiskit-neko@main
         with:
           test_selection: terra
-          repo_install_command: "pip install -c constraints.txt ."
+          # We have to forcibly uninstall any old version of qiskit or qiskit-terra during the
+          # changeover, because it's not possible to safely switch between 0.46 and 1.0.
+          repo_install_command: "pip uninstall -y qiskit qiskit-terra && pip install -c constraints.txt . ./qiskit_pkg"