Remove unused TK_tagged_opt production

Signed-off-by: Krzysztof Bieganski <kbieganski@antmicro.com>

verible/verilog/parser/verilog.y

diff --git a/verible/verilog/parser/verilog.y b/verible/verilog/parser/verilog.y
index 00c2ead..ef746fd 100644
--- a/verible/verilog/parser/verilog.y
+++ b/verible/verilog/parser/verilog.y
@@ -7378,12 +7378,6 @@
   | /* empty */
     { $$ = nullptr; }
   ;
-TK_tagged_opt
-  : TK_tagged
-    { $$ = std::move($1); }
-  | /* empty */
-    { $$ = nullptr; }
-  ;
 TK_union_qualifier_opt
   : TK_soft
     { $$ = std::move($1); }