Apply suggestions from code review

Co-authored-by: Dongdong Tian <seisman.info@gmail.com>

Author: Meghan Jones

pygmt/src/grdimage.py

@@ -133,7 +133,7 @@ def grdimage(self, grid, **kwargs):
         intensity, and ambient arguments for that module, or just give
         **+d** to select the default arguments
         [Default is **+a**\ -45\ **+nt**\ 1\ **+m**\ 0]. If you want a more
-        specific intensity scenario then run `grdgradient` separately first. If
+        specific intensity scenario then run ``grdgradient`` separately first. If
         we should derive intensities from another file than grid, specify the
         file with suitable modifiers [Default is no illumination].
     {J}

pygmt/src/grdview.py

@@ -104,7 +104,7 @@ def grdview(self, grid, **kwargs):
         **+a**\ *azimuth*, **+n**\ *args*, and **+m**\ *ambient* to specify
         azimuth, intensity, and ambient arguments for that module, or just give
         **+d** to select the default arguments
-        [default is **+a**\ -45\ **+nt**\ 1\ **+m**\ 0].
+        [Default is **+a**\ -45\ **+nt**\ 1\ **+m**\ 0].
     {V}
     {XY}
     {c}