Bump merged_s2s version following strax.merge_peaks

[dachengx]

What does the code in this PR do / what does it improve?

Following PR https://github.com/AxFoundation/stax/pull/722

Can you briefly describe how it works?

Can you give a minimal working example (or illustrate with a figure)?

Please include the following if applicable:

• Update the docstring(s)
• Update the documentation
• Tests to check the (new) code is working as desired.
• Does it solve one of the open issues on github?

Notes on testing

• Until the automated tests pass, please mark the PR as a draft.
• On the XENONnT fork we test with database access, on private forks there is no database access for security considerations.

All italic comments can be removed from this template.

[coveralls]

Coverage: 93.437% (-0.01%) from 93.447% when pulling 46967b3 on bump_merged_s2s_722 into 78bd324 on master.