temp: pin boto3 to 1.34.115

[robrap]

We're getting a failure for missing 1.34.116, and not sure if the lack of pin is what is allowing for it to be requested.

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Make sure that the following steps are done before merging:

• Have a Site Reliability Engineer review the PR if you don't own all of the services impacted.
• If you are adding any new default values that need to be overridden when this change goes live, update internal repos and add an entry to the top of the CHANGELOG.
• Performed the appropriate testing.

[timmc-edx]

I suspect this will work because boto3/botocore 1.34.116 was just released, and there's probably a stale index not allowing the botocore dependency to be fetched. (boto3 requires the most recent botocore.)

[timmc-edx]

Reverting here: #60