Removing rvfi assert on illegal instruction

The reason for removing this assert is that any custom instructions
or custom extensions would trigger this assert. It does not really
verify the rvfi interface, but forces all instruction to be added
to the dissassembler.

tb/assertions/uvmt_cv32e40x_rvfi_assert.sv

@@ -349,14 +349,6 @@ module uvmt_cv32e40x_rvfi_assert
   ) else `uvm_error(info_tag, "!store->!exce, exce->store");
 
 
-  // Disassembler
-
-  a_unknowninstr_trap: assert property (
-    (rvfi_if.instr_asm.instr == UNKNOWN_INSTR) && rvfi_if.rvfi_valid
-    |->
-    rvfi_if.rvfi_trap.trap
-  ) else `uvm_error(info_tag, "Unknown instruction is not trapped");
-
 // RV32E
   if (RV32 == cv32e40x_pkg::RV32E) begin: gen_rv32e_rd1
     a_rvfi_rd1_rv32e: assert property(