fix typo

Co-authored-by: Copilot <[email protected]>

Author: Jemoka

stanza/utils/datasets/coref/convert_udcoref.py

@@ -129,7 +129,7 @@ def process_documents(docs, augment=False):
                 if sentence_text[span[1]] == "_" and span[1] == span[2]:
                     is_zero.append([span[0], True])
                     zero = True
-                    # oo! thaht's a zero coref, we should merge it forwards 
+                    # oo! that's a zero coref, we should merge it forwards 
                     # i.e. we pick the next word as the head!
                     span = [span[0], span[1]+1, span[2]+1]
                     # crap! there's two zeros right next to each other