refactor: shorten preventSigmaIncrease to limitSigma

[philihp]

renames this to be in line with openskill.py. old way will still work for a while.

cc: @vivekjoshy

[coveralls]

coverage: 99.359% (-0.6%) from 100.0%
when pulling 319980e on renameLimitSigma
into bf96347 on main.

[coveralls]

coverage: 99.359% (-0.6%) from 100.0%
when pulling 319980e on renameLimitSigma
into bf96347 on main.

[coveralls]

coverage: 100.0%. remained the same
when pulling 9b28989 on renameLimitSigma
into bf96347 on main.

[coveralls]

coverage: 100.0%. remained the same
when pulling e4297c8 on renameLimitSigma
into bf96347 on main.

[coveralls]

coverage: 100.0%. remained the same
when pulling 07c5f77 on renameLimitSigma
into 960b039 on main.

[coveralls]

coverage: 100.0%. remained the same
when pulling b2e3832 on renameLimitSigma
into 960b039 on main.