cranelift: Remove brz and brnz (#5630)

Remove the brz and brnz instructions, as their behavior is now redundant with brif.

cranelift/codegen/src/isa/riscv64/inst/args.rs

@@ -118,7 +118,6 @@ impl Into<AMode> for StackAMode {
 }
 
 /// risc-v always take two register to compare
-/// brz can be compare with zero register which has the value 0
 #[derive(Clone, Copy, Debug)]
 pub struct IntegerCompare {
     pub(crate) kind: IntCC,

cranelift/codegen/src/isa/riscv64/inst/unwind/systemv.rs

@@ -159,8 +159,7 @@ mod tests {
 
         let mut pos = FuncCursor::new(&mut func);
         pos.insert_block(block0);
-        pos.ins().brnz(v0, block2, &[]);
-        pos.ins().jump(block1, &[]);
+        pos.ins().brif(v0, block2, &[], block1, &[]);
 
         pos.insert_block(block1);
         pos.ins().return_(&[]);