Updating hypre reference

src/docs/JOSS/paper.bib

@@ -48,12 +48,14 @@ @article{Beckingsale:2020
 year = {2020}
 }
 
-@misc{hypre,
-  key   =       {hypre},
-  title =       {{\sl hypre}: High Performance Preconditioners},
-  journal = {GitHub repository},
-  url = {\url{https://llnl.gov/casc/hypre}, \url{https://github.com/hypre-space/hypre}}
-  }
+@InProceedings{hypre,
+    author = {R. D. Falgout and U.M. Yang},
+    title = {\textit{hypre}: a Library of High Performance Preconditioners},
+    booktitle = {Lecture Notes in Computer Science},
+    year = {2002},
+    pages = {632--641},
+    doi={10.1007/3-540-47789-6_66}
+}