fix syntax error in generics.bib

Author: JCSooHwanCho

docs/Generics/generics.bib

@@ -300,7 +300,7 @@ @inproceedings{essential
 isbn = {1595930566},
 publisher = {Association for Computing Machinery},
 address = {New York, NY, USA},
-url = {https://www.researchgate.net/publication/213886648_Essential_Language_Support_for_Generic_Programming}
+url = {https://www.researchgate.net/publication/213886648_Essential_Language_Support_for_Generic_Programming},
 doi = {10.1145/1065010.1065021},
 booktitle = {Proceedings of the 2005 ACM SIGPLAN Conference on Programming Language Design and Implementation},
 pages = {73–84},