Remove bogus quotes from example usage of set= option

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@31471 15284696-431f-4ddb-bdfa-cd5b030d7da7

general/g.gisenv/main.c

@@ -48,7 +48,7 @@ int main(int argc, char *argv[])
     set->key          = "set" ;
     set->type         = TYPE_STRING ;
     set->description  = _("GRASS variable to set") ;
-    set->key_desc     = "\"VARIABLE=value\"" ;
+    set->key_desc     = "VARIABLE=value" ;
     set->required     = NO;
 
     store_opt               = G_define_option() ;