docs: fix invalid reference formatting for infomap

Author: szhorvat

src/_igraph/graphobject.c

@@ -18455,8 +18455,8 @@ struct PyMethodDef igraphmodule_Graph_methods[] = {
    "Finds the community structure of the network according to the Infomap\n"
    "method of Martin Rosvall and Carl T. Bergstrom.\n\n"
    "See U{https://www.mapequation.org} for a visualization of the algorithm\n"
-   "or one of the references provided below.\n"
-   "B{Reference}: "
+   "or one of the references provided below.\n\n"
+   "B{References}\n\n"
    "  - M. Rosvall and C. T. Bergstrom: I{Maps of information flow reveal\n"
    "    community structure in complex networks}. PNAS 105, 1118 (2008).\n"
    "    U{https://arxiv.org/abs/0707.0609}\n"