Remove scheduled runs of the CI GPU workflows

[rasa-jmac]

Proposed changes:

• Disable the CI workflows that deploy + use GPUs on GCP.
• Additionally, I've disabled the GCP service accounts that these workflows used.

Status (please check what you already did):

• [ ] added some tests for the functionality
• [ ] updated the documentation
• [ ] updated the changelog (please check changelog for instructions)
• [ ] reformat files using black (please check Readme for instructions)