[Launcher] Remove derby jars from ext folder (now bundled in databasePersistence)

Follows up on nasa/mct#143 and nasa/mct#144

Derby jars are now packaged in databasePersistence. Previously, these were added to the "ext" folder, but now this is redundant. This change removes these from the maven build for the distribution, saving ~3MB of file size.

 Wrote or re-wrote unit tests (Y/N): N/A
 Ran entire suite of unit tests successfully (Y/N): Y
 Verified bug fix with the described replication steps or verified the implementation meets the requirement cited (Y/N): N/A
 Code coverage requirements satisfied (new code=80%, changed code=at least as high as existing) (Y/N): N/A
 Code review date and attendees: Code review by pull request
 Describe potential impact on other areas of the code: Persistence
 Describe any test prerequisites for this fix (e.g., restart the database): Build and run distribution using derby
 For bugs marked "Regression - Yes", describe the cause of the regression: N/A
 Did you modify any pom.xml file? If yes, did you thoroughly document your changes and reasons? Y

Unit testing requirements are not applicable to this change; only the distribution assembly has been modified