DOC: Fix syntax of aliases list for pygmt.grdtrack, pygmt.x2sys_cross (#4115)

Author: yvonnefroehlich

pygmt/src/grdtrack.py

@@ -79,7 +79,7 @@ def grdtrack(
     Full GMT docs at :gmt-docs:`grdtrack.html`.
 
     {aliases}
-        - V = verbose
+       - V = verbose
 
     Parameters
     ----------

pygmt/src/x2sys_cross.py

@@ -92,7 +92,7 @@ def x2sys_cross(
     Full GMT docs at :gmt-docs:`supplements/x2sys/x2sys_cross.html`.
 
     {aliases}
-        - V = verbose
+       - V = verbose
 
     Parameters
     ----------