refactor: [WFE.setup()] remove unneeded input file check

Check for missing input files not needed as object cannot be initialised without them

pipeline/feature_extractors.py

@@ -444,10 +444,6 @@ class WordFeatureExtractor(FeatureExtractor):
         """
         logger.debug("WordFeatureExtractor setup")
 
-        # Validate input files
-        if not self.input_files:
-            raise ValueError("No input files provided")
-
         # Validate words - raise a notice if none provided
         if len(words) == 0:
             logger.warning("No words provided for detection")