Update dependency scope for DB backends

[nickrobison]

When upgrading a project from Quartz 2.3.2 to 2.5.0 we ran into the following error:

Exception in thread "main" java.lang.NoClassDefFoundError: com/mchange/v2/c3p0/ComboPooledDataSource
	at org.quartz.utils.C3p0PoolingConnectionProvider.initialize(C3p0PoolingConnectionProvider.java:187)
	at org.quartz.utils.C3p0PoolingConnectionProvider.<init>(C3p0PoolingConnectionProvider.java:106)
	at com.rms.mapping.system.scheduler.QuartzSchedulerManager$.init(QuartzSchedulerManager.scala:225)
	at com.rms.mapping.system.scheduler.QuartzSchedulerManager$.apply(QuartzSchedulerManager.scala:201)

Looking at the Gradle build, it look like the c3p0 dependency is declared as implementation which means it's not exposed on the runtime class path. While the workaround from #1310 is sufficient if these types are exposed in the library API then it seems to make sense to change their declaration scope.

This PR updates the dependency declaration to restore the behavior of the 2.3.x library.

If these dependencies were intentionally hidden then perhaps a comment in the release notes or the README would be helpful?

Fixes issue #1310

Changes

• Update Gradle dependency scope

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Checklist

• tested locally
• updated the docs
• added appropriate test
• signed-off on the DCO referenced in the CONTRIBUTING link below via git commit -s on my commits, and submit this code under terms of the Apache 2.0 license and assign copyright to the Quartz project owners
  (If you're not using command-line, you can use a browser extension )

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In submitting this contribution, I agree to the terms of contributing as referred to here:
https://github.com/quartz-scheduler/contributing/blob/main/CONTRIBUTING.md

[jhouserizer]

It was intentional - but with some hesitation. In light of your report I will review/ponder.

[jhouserizer]

The concerns here are:

• More than half of the users of Quartz use JDBCJobStore and hence end up needing these dependencies. So its arguably a regression not to.
• A large portion (but a bit less than half) of Quartz users are using RAMJobStore and don't want these dependencies dragged in. So it's an improvement not to.

[jhouserizer]

Also relates to #1384

[jhouserizer]

Hi after consideration, and discussion with a couple of others, I don't believe this change can / should be made in a dot release. Especially considering there is another set of users that would be annoyed in the opposite direction. Also if we were to take care of the one you mentioned, there are several others that should be reviewed.

Will prepare some comments to add to the release notes and/or installation docs to help users out. Thanks for reporting.

[jhouserizer]

Deferring for now.