Wrap maybe function in quotes, so it is treated as an atom (backport #11251)

[mergify]

Proposed Changes

Since maybe is added as an optional keyword in OTP 25, quote its usage as an atom, so that it does not break syntax highlighting and other language service features.

Types of Changes

What types of changes does your code introduce to this project?

• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI

Checklist

• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• I have added tests that prove my fix is effective or that my feature works
• All tests pass locally with my changes
• If relevant, I have added necessary documentation to https://github.com/rabbitmq/rabbitmq-website
• If relevant, I have added this change to the first version(s) in release-notes that I expect to introduce it

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This is an automatic backport of pull request #11251 done by [Mergify](https://mergify.com).

[michaelklishin]

Not merging yet until next week when a Tanzu RabbitMQ release ships, then we will be ready to re-start backports of PRs that change the code (that is, not the build system parts or docs, for example).