grammar: do not add a \n at the end of blocks of code

Now that we use "braceless" (which is {...} blocks of code with
initial and final braces stripped) to denote "short" values (such as
api.namespaces), the added end-of-line is a nuisance.  As a matter of
fact, this extra-safety was useless, as every expansion of "braceless"
(aka, "user code") is followed by an end of line.

* src/parse-gram.y, src/parse-gram.c (braceless): Instead of replacing
the final brace by \n, just delete the brace.

src/parse-gram.c

@@ -2676,7 +2676,7 @@ yyreduce:
 #line 683 "src/parse-gram.y" /* yacc.c:1668  */
     {
       code_props plain_code;
-      (yyvsp[0].code)[strlen ((yyvsp[0].code)) - 1] = '\n';
+      (yyvsp[0].code)[strlen ((yyvsp[0].code)) - 1] = '\0';
       code_props_plain_init (&plain_code, (yyvsp[0].code)+1, (yylsp[0]));
       code_props_translate_code (&plain_code);
       gram_scanner_last_string_free ();

src/parse-gram.y

@@ -682,7 +682,7 @@ braceless:
   "{...}"
     {
       code_props plain_code;
-      $1[strlen ($1) - 1] = '\n';
+      $1[strlen ($1) - 1] = '\0';
       code_props_plain_init (&plain_code, $1+1, @1);
       code_props_translate_code (&plain_code);
       gram_scanner_last_string_free ();