Adds test for AdjMatrix

Author: tanishy7777

pydatastructs/graphs/tests/test_algorithms.py

@@ -449,3 +449,4 @@ def _test_max_flow(ds, algorithm):
     _test_max_flow("List", "dinic")
     _test_max_flow("Matrix", "dinic")
     _test_max_flow("List", "ford_fulkerson")
+    _test_max_flow("Matrix", "ford_fulkerson")