fix: use ops 2.17.1 in the mock charm

[gatici]

Description

Install hook in the mock charm is failing to find scenario.runtime which is imported from ops.
This causes failure in integration tests.
The scenario.runtime library relies on ops==2.17.x.
Latest version of ops have breaking changes that make these libraries incompatible.

As a workaround we need to pin the ops version until incompatibilities are solved in the dependent projects.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that validate the behaviour of the software
• I validated that new and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have bumped the version of the library