Fix docs typo
Fix docs typo

use the passed `mapFilePath` variable, instead of `mapFile`.
floridoo/gulp-sourcemaps,floridoo/gulp-sourcemaps,gulp-sourcemaps/gulp-sourcemaps,floridoo/gulp-sourcemaps,gulp-sourcemaps/gulp-sourcemaps,gulp-sourcemaps/gulp-sourcemaps,realtymaps/gulp-sourcemaps,realtymaps/gulp-sourcemaps,realtymaps/gulp-sourcemaps