STYLE: Coverity 1080839: Dead default in switch in QuadEdgeMeshEulerOperatorJoinVertexTest

The code above the switch statement verifies that InputType is within
[0, 5]. The switch statement contains labels for all values [0, 5], so a
default statement is unnecessary.

This is not strictly a bug, as the behavior is unchanged.

Change-Id: I6e8b4494688161b9b4d45b6e4044375dd4552d2a
Merge topic 'cov_1080839'

0a08acb0 STYLE: Coverity 1080839: Dead default in switch in QuadEdgeMeshEulerOperatorJoinVertexTest