as seen in bug 95928 this used to be locked at 1 but was lowered
to 0.1 as acceleration != speed, so <1 makes perfect sense.
however, by extension, 0.0 also makes sense (no acceleration on
top of hardware input) which I think was an oversight in the
original decrease.
this change sets the lower bounds of the input field to 0.0 so
one can effectively disable acceleration
CHANGELOG: Mouse settings now allow setting acceleration to 0.0