Add note on operator precedence to opflow docs (#7195)
Add note on operator precedence to opflow docs (#7195)

* Add note on operator precedence to opflow docs

I've tried to match the style of the language used in the rest of the
documentation for this.

* Add exact example of brackets

Co-authored-by: Julien Gacon <2578673985e8ae3d22330d3daafe06433268eaa0@gmail.com>

Co-authored-by: Julien Gacon <2578673985e8ae3d22330d3daafe06433268eaa0@gmail.com>
Co-authored-by: mergify[bot] <b09a6ee808b67e98a221404e7aaa52e0398a4954@users.noreply.github.com>
QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py