Add support for MulanPSL-2.0 in license detection

Adds support for MulanPSL-2.0 in license detection of a project by updating licensee gem from 9.14.1 to 9.15.2.

Counterpart PR in gitlab: gitlab!94948 (merged)

Closes gitlab#369444 (closed)

Signed-off-by: Takuya Noguchi takninnovationresearch@gmail.com Changelog: other