Use "database_connection" within a context-manager
Use "database_connection" within a context-manager

Using "database_connection" within a context-manager makes sure that
the SQL connection that is created is closed.

* wqflask/wqflask/metadata_edits.py (display_probeset_metadata):
Connect to the db within a context-manager.
(update_phenotype): Ditto.
(update_probeset): Ditto.
(approve_data): Ditto.

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