Remove additional classes on GLTokenSelector

What does this MR do and why?

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As per this comment, to remove the visual issue of vertical alignment, the decision was to remove to the fixed height of this GlTokenSelector. Once the fixed height is removed, the gl-overflow-y-auto is no longer relevant either.

Also removing gl-overflow-y-auto in menu classes as it is automatically added within GlTokenSelector.

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Related to #344950 (closed)