Fix two typos in comments.

contrib/cube/cubeparse.y

@@ -10,7 +10,7 @@
 
 #include "cubedata.h"
 
-#undef yylex                 /* falure to redefine yylex will result in a call to  the */
+#undef yylex                 /* failure to redefine yylex will result in a call to  the */
 #define yylex cube_yylex     /* wrong scanner when running inside the postgres backend  */
 
 extern int yylex(void);      /* defined as cube_yylex in cubescan.l */

contrib/seg/segparse.y

@@ -7,7 +7,7 @@
 
 #include "segdata.h"
 
-#undef yylex                  /* falure to redefine yylex will result in calling the */
+#undef yylex                  /* failure to redefine yylex will result in calling the */
 #define yylex seg_yylex       /* wrong scanner when running inside postgres backend  */
 
   extern int yylex(void);     /* defined as seg_yylex in segscan.l */