DOC: Improve highlighting for pygmt.nearneighbor (#4424)

Author: yvonnefroehlich

pygmt/src/nearneighbor.py

@@ -45,7 +45,7 @@ def nearneighbor(
     r"""
     Grid table data using a "Nearest neighbor" algorithm.
 
-    **nearneighbor** reads arbitrarily located (*x*, *y*, *z*\ [, *w*])
+    :func:`pygmt.nearneighbor` reads arbitrarily located (*x*, *y*, *z*\ [, *w*])
     triplets [quadruplets] and uses a nearest neighbor algorithm to assign a
     weighted average value to each node that has one or more data points within
     a search radius centered on the node with adequate coverage across a subset