fix(store): rename template literal to string literal for createActionGroup

[markostanimirovic]

PR Checklist

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• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Template literals are subsets of string literal types. The createActionGroup function requires to use string literals for source/event names, but the error message is 'source/event name must be a template literal type'.

What is the new behavior?

Displaying correct error message when the type of source/event name is not a string literal.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[brandonroberts]

@markostanimirovic do we need to backport this fix to 13.2 also?

[markostanimirovic]

@brandonroberts I don't think it's necessary, because it fixes the error message only.