Rename wxGridBlockCoords::ContainsCell/Block() to just Contains()

These methods do the same thing, so it seems better to use the same name
for them.

This is not really a backwards-incompatible change, as these methods
were just added in the parent commit, so nobody is using them yet.

interface/wx/grid.h

@@ -1921,7 +1921,7 @@ public:
         @return
             @true, if the block contains the cell, @false otherwise.
      */
-    bool ContainsCell(const wxGridCellCoords& cell) const;
+    bool Contains(const wxGridCellCoords& cell) const;
 
     /**
         Check whether this block contains another one.
@@ -1929,7 +1929,7 @@ public:
         @return
             @true if @a other is entirely contained within this block.
      */
-    bool ContainsBlock(const wxGridBlockCoords& other) const;
+    bool Contains(const wxGridBlockCoords& other) const;
 
     /**
         Calculates the result blocks by subtracting the other block from this