grabbing_sheets -> sheet_grab

BUR #3021 has been approved by @evazion.

create alias grabbing_sheet -> sheet_grab

Same thing; the former(s) is also easy to add by accident instead of the latter.

EDIT: The bulk update request #3021 (forum #169320) has been approved by @evazion.

sheet grab already shows up in the suggestion list when typing "grabbing_sh". Same for other tags like grabbing_arm -> arm grab.

The bulk update request #3021 (forum #169320) has been approved by @evazion.