Typo fixes

Co-Authored-By: Dongdong Tian <seisman.info@gmail.com>

pygmt/src/nearneighbor.py

@@ -103,12 +103,13 @@ def nearneighbor(data=None, x=None, y=None, z=None, **kwargs):
         into *sectors* sectors. Average values will only be computed if there
         is *at least* one value inside each of at least *min_sectors* of the
         sectors for a given node. Nodes that fail this test are assigned the
-        value NaN (but see ``empty``). If +m is omitted then *min_sectors* is
-        set to be at least 50% of *sectors* (i.e., rounded up to next integer)
-        [Default is a quadrant search with 100% coverage, i.e., *sectors* =
-        *min_sectors* = 4]. Note that only the nearest value per sector enters
-        into the averaging; the more distant points are ignored. Alternatively,
-        use ``sectors="n"`` to call GDALʻs nearest neighbor algorithm instead.
+        value NaN (but see ``empty``). If **+m** is omitted then *min_sectors*
+        is set to be at least 50% of *sectors* (i.e., rounded up to next
+        integer) [Default is a quadrant search with 100% coverage, i.e.,
+        *sectors* = *min_sectors* = 4]. Note that only the nearest value per
+        sector enters into the averaging; the more distant points are ignored.
+        Alternatively, use ``sectors="n"`` to call GDAL's nearest neighbor
+        algorithm instead.
 
     {V}
     {a}