Update inst_format.gbnf

inst_format.gbnf

@@ -1,5 +1,5 @@
 # GBNF grammar for [INST] format
-root ::= "[INST]\n### System:\n" ws system "\n### Instruction:\n" ws instruction "\n[/INST]\n"
+root ::= "[INST]\n### System:\n"system"\n### Instruction:\n"instruction"\n[/INST]\n"
 
 # `system` represents the system information
 system ::= string
@@ -8,10 +8,10 @@ system ::= string
 instruction ::= string
 
 string ::=
-  "\"" (
+  "" (
     [^"\\] |
     "\\" (["\\/bfnrt] | "u" [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F]) # escapes
-  )* "\"" ws
+  )* "" ws
 
 
 # Optional space: by convention, applied in this grammar after literal chars when allowed