Fix error computing tertiary hue

After adding 60 degrees to the hue, the result needs to be normalized to
0 to 360. Code downstream of Shades.of does not perform the
normalization, so the resulting color will be the result of undefined
behavior.

Test: `atest ColorSchemeTest`, newly added testTertiaryHueWrapsProperly
passes.
Bug: 204463343

Change-Id: I93168c98ba64fb865888469220571dc6d437105d