pki: Increase MAX_LINES

The --issue and --self commands both define 10 lines of usage summary
text.

src/pki/command.h

@@ -34,7 +34,7 @@
 /**
  * Maximum number of usage summary lines (+1)
  */
-#define MAX_LINES 10
+#define MAX_LINES 11
 
 typedef struct command_t command_t;
 typedef struct command_option_t command_option_t;