Fix comment typos

Author: haohangyan

indra/literature/pmc_client.py

@@ -279,7 +279,7 @@ def _extract_from_pmc_ocr(tree):
             continue
 
         text = "".join(pre.itertext())
-        # Remove xml BOM and unify newline format
+        # Remove xml BOM and unify newline formats
         text = text.replace("\ufeff", "")
         text = text.replace("\r\n", "\n").replace("\r", "\n")