Specify help icon link color

This is aiming to align and specify the color of the ? icon when linking to documentation (or additional help). Our text link/anchors are colored #1068bf, however, we are seeing inconsistencies when using ? (often blue, sometimes grey/black even when linking to documentation).

Examples of ? with differing colors, but anchor to documentation. As discussed in gitlab-org/gitlab#199053 (comment 326569720)

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