fix: ensure newline at end of file in standardize_quotes function

Author: christinestraub

unstructured/metrics/text_extraction.py

@@ -236,4 +236,4 @@ def standardize_quotes(text: str) -> str:
         if unicode_char in text:
             text = text.replace(unicode_char, single_quote_standard)
 
-    return text
+    return text