[wasm][eh] Remove BranchOnExceptionImmediate

This was only relevant for the br_on_exn instruction, which doesn't
exist anymore.

R=clemensb@chromium.org

Change-Id: I03f85a316a8265ad1c5e1c15862d7ae98b784977
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2902734Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74641}

src/wasm/function-body-decoder-impl.h

@@ -574,18 +574,6 @@ struct BranchDepthImmediate {
   }
 };
 
-template <Decoder::ValidateFlag validate>
-struct BranchOnExceptionImmediate {
-  BranchDepthImmediate<validate> depth;
-  ExceptionIndexImmediate<validate> index;
-  uint32_t length = 0;
-  inline BranchOnExceptionImmediate(Decoder* decoder, const byte* pc)
-      : depth(BranchDepthImmediate<validate>(decoder, pc)),
-        index(ExceptionIndexImmediate<validate>(decoder, pc + depth.length)) {
-    length = depth.length + index.length;
-  }
-};
-
 template <Decoder::ValidateFlag validate>
 struct FunctionIndexImmediate {
   uint32_t index = 0;
@@ -1495,13 +1483,6 @@ class WasmDecoder : public Decoder {
     return checkAvailable(imm.table_count);
   }
 
-  inline bool Validate(const byte* pc,
-                       BranchOnExceptionImmediate<validate>& imm,
-                       size_t control_size) {
-    return Validate(pc, imm.depth, control_size) &&
-           Validate(pc + imm.depth.length, imm.index);
-  }
-
   inline bool Validate(const byte* pc, WasmOpcode opcode,
                        SimdLaneImmediate<validate>& imm) {
     uint8_t num_lanes = 0;