Update pmc.py

pmc.py

@@ -94,7 +94,7 @@ def extract_pmc_data():
     for topic, pmcids in pmcid_data.items():
         pmc_ids = []
         for id in pmcids:
-            if len(pmc_ids) >= 2:
+            if len(pmc_ids) >= 3:
                 continue
             elif tools.check_data_in_file(id, 'pmc.txt'):
                 continue