Remove an unused param from InputMethodSettings constructor

"methodList" parameter in the constructor of InputMethodSettings is
not used.  This CL removes it in favor of simplicity.

This is a mechanical refactoring.  There should be no behavior change.

Bug: 123379418
Test: make -j checkbuild
Test: atest CtsInputMethodTestCases CtsInputMethodServiceHostTestCases
Change-Id: Ifd987bf57d6ed5622e9091157b1933f6da3ff181