Remove workaround for J2CL + Character.isLetter incompatibility

We've removed the J2CL build of JSCompiler so this workaround is no longer necessary.

PiperOrigin-RevId: 707700404

src/com/google/javascript/jscomp/parsing/parser/Identifiers.java

@@ -30,25 +30,7 @@ public static boolean isIdentifierStart(char ch) {
 
     // Handle non-ASCII characters.
     // TODO(tjgq): This should include all characters with the ID_Start property.
-    if (Character.isLetter(ch)) {
-      return true;
-    }
-
-    // Workaround for b/36459436.
-    // When running under GWT/J2CL, Character.isLetter only handles ASCII.
-    // Angular relies heavily on Latin Small Letter Barred O and Greek Capital Letter Delta.
-    // Greek letters are occasionally found in math code.
-    // Latin letters are found in our own tests.
-    return (ch >= 0x00C0 & ch <= 0x00D6) // Latin letters
-        // 0x00D7 = multiplication sign, not a letter
-        | (ch >= 0x00D8 & ch <= 0x00F6) // Latin letters
-        // 0x00F7 = division sign, not a letter
-        | (ch >= 0x00F8 & ch <= 0x00FF) // Latin letters
-        | ch == 0x0275 // Latin Barred O
-        | (ch >= 0x0391 & ch <= 0x03A1) // Greek uppercase letters
-        // 0x03A2 = unassigned
-        | (ch >= 0x03A3 & ch <= 0x03A9) // Remaining Greek uppercase letters
-        | (ch >= 0x03B1 & ch <= 0x03C9); // Greek lowercase letters
+    return Character.isLetter(ch);
   }
 
   @SuppressWarnings("ShortCircuitBoolean") // Intentional to minimize branches in this code

src/com/google/javascript/jscomp/regex/RegExpTree.java

@@ -748,12 +748,7 @@ private static boolean isIdentifierStart(char ch) {
       return ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch == '_' || ch == '$'));
     }
 
-    // Workaround b/36459436
-    // When running under GWT, Character.isLetter only handles ASCII
-    // Angular relies heavily on U+0275 (Latin Barred O)
-    return ch == 0x0275
-        // TODO: UnicodeLetter also includes Letter Number (NI)
-        || Character.isLetter(ch);
+    return Character.isLetter(ch);
   }
 
   /**