Fix assignment indentation in ToolkitGdTest

Problem/Motivation

Reviewing #2687941: [Policy, no patch] Within the Function Calls section, delete explicit mention of padding spacing in a block of related assignments → I noticed the indention for the colors was not aligned. Additionally while the // Used as rotate background colors comment was relevant to the patch it came in with, those colors are just colors available to the testing class and could be used for anything in additional tests. The comment just duplicates what's actually implemented.

Proposed resolution

Fix it indentation and remove confusing comment.

Remaining tasks

#2687941: [Policy, no patch] Within the Function Calls section, delete explicit mention of padding spacing in a block of related assignments → may block or invalidate this?

User interface changes

N/A

API changes

N/A

Data model changes

N/A