STYLE: grammer fix

Source/cmMessageCommand.h

@@ -69,7 +69,7 @@ public:
       "By default the message is displayed in a pop up window (CMakeSetup), "
       "or in the stdout of cmake, or the error section of ccmake. "
       "If the first argument is "
-      "SEND_ERROR then an error is raised, and the generate phase will be "
+      "SEND_ERROR then an error is raised, and the generate phase will "
       "be skipped.  If the first argument is FATAL_ERROR, all processing "
       "is halted. If the first argument is STATUS then the message is "
       "displayed in the progress line for the GUI, or with a -- in the "