We were being inconsistent with calling Runtime "Qiskit Runtime IBM
Client" but "Qiskit IBM Runtime REST API". We also don't use IBM with
"Qiskit Transpiler Service Client" and "Qiskit SDK". So, `@jyu00` and
`@javabster` proposed that we simplify to remove the redundant IBM.
This PR updates the left page titles we use. A closed source PR will
update the top dropdown.
We don't update the index pages for Runtime API docs because those are
auto-generated.
0c8bd4190f