Blender Git Loki

Fix T81069: Can't lock axis with move anymore, using Shift+MMB

This fixes and reverts commit c7287ffaec59cecd4b63b4bb2ea1aaf44f09f704

Due to hardcodded keys, the modifier for auto contrain plane did not
work with custom keymaps and was in conflict with other keyitems.

Its usability is also confusing since it cannot be used without
`MOD_PRECISION`

But instead of removing it, it is better to make this modifier compatible
with custom keymaps and keep the conflict.