Temporarily use git for qasm3 import

In Qiskit/qiskit-qasm3-import#34 the issue we're hitting caused by
qiskit-qasm3-import using the private circuit attributes removed in this
PR was fixed. This commit temporarily moves to installing it from git so
we can fully run CI. When qiskit-qasm3-import is released we should
revert this commit.

requirements-optional.txt

@@ -19,7 +19,7 @@ seaborn>=0.9.0
 
 # Functionality and accelerators.
 qiskit-aer
-qiskit-qasm3-import
+qiskit-qasm3-import @ git+https://github.com/Qiskit/qiskit-qasm3-import
 python-constraint>=1.4
 cvxpy
 scikit-learn>=0.20.0