Updated obsolete FileTypeCheckStateIsDirty to the new name BeforeBackgroundFileCheck
Updated obsolete FileTypeCheckStateIsDirty to the new name BeforeBackgroundFileCheck

Missed this with the last PR for FSharp.Compiler.Service API changes.

cloudRoutine/FsAutoComplete,kjnilsson/FSharp.AutoComplete,cloudRoutine/FsAutoComplete,vasily-kirichenko/FsAutoComplete,rneatherway/FsAutoComplete