fix(ng-doc/component-groups-generate processor): use paths from configuration

paths were hardcoded in the ngdoc: comopnent group generator, updated to use the paths from the configuration (processing.api-docs).

this will only cause issues if you had changed processing.api-docs.path or processing.api-docs.outputPath and still expect the component groups to be output in the hardcoded location (which probably doesn't make sense?).

with default settings this will produce the same result.