fixed warning: stray ',' at the end of enum

Signed-off-by: Sergei Trofimovich <slyfox@inbox.ru>

src/subshell.c

@@ -137,7 +137,7 @@ static enum {
     BASH,
     TCSH,
     ZSH,
-    FISH,
+    FISH
 } subshell_type;
 
 /* Flag to indicate whether the subshell is ready for next command */