Remove out of date constraints from constraints.txt (#7154)
Remove out of date constraints from constraints.txt (#7154)

The constraints.txt file is used to pin specific versions of packages in
the dependency tree when we can't (typically for dependencies of
dependencies) modify the requirements list to workaround temporary
packaging issues. With the recent release of stevedore 3.5.0 [1] the
importlib-metadata pin in the constraints.txt file was no longer needed.
However, looking at the git log for other pinned dependencies only 1
package being pinned is still required, jsonschema, because nbformat
hasn't been updated to fix the incompatibility with the latest version
yet. This commit removes all the out of date entries from the
constraints.txt file leaving only the pin for jsonschema so we're
testing the latest versions of everything in CI, so that our CI
environment is closer to what users will typically install.

[1] https://pypi.org/project/stevedore/3.5.0/
QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py