Fix a typo

pointed out in https://github.com/google/turbine/pull/221/files/5fa092b3e62d407b9355a2740b4aab6750ef174d#r827285242

PiperOrigin-RevId: 434894676
diff --git a/java/com/google/turbine/parse/Token.java b/java/com/google/turbine/parse/Token.java
index 7d20beb..ec214a5 100644
--- a/java/com/google/turbine/parse/Token.java
+++ b/java/com/google/turbine/parse/Token.java
@@ -23,8 +23,8 @@
   RPAREN(")"),
   LBRACE("{"),
   RBRACE("}"),
-  LBRACK("<"),
-  RBRACK(">"),
+  LBRACK("["),
+  RBRACK("]"),
   EOF("<eof>"),
   SEMI(";"),
   COMMA(","),