update to 1.21 in a few more places

CONTRIBUTING.md

@@ -56,7 +56,7 @@ The gno repository is primarily based on Go (Golang) and Gno.
 
 The primary tech stack for working on the repository:
 
-- Go (version 1.20+)
+- Go (version 1.21+)
 - make (for using Makefile configurations)
 
 It is recommended to work on a Unix environment, as most of the tooling is built around ready-made tools in Unix (WSL2

gnovm/cmd/gno/test.go

@@ -174,7 +174,7 @@ func execTest(cfg *testCfg, args []string, io commands.IO) error {
 
 	// go.mod
 	modPath := filepath.Join(tempdirRoot, "go.mod")
-	err = makeTestGoMod(modPath, gno.ImportPrefix, "1.20")
+	err = makeTestGoMod(modPath, gno.ImportPrefix, "1.21")
 	if err != nil {
 		return fmt.Errorf("write .mod file: %w", err)
 	}

gnovm/stdlibs/std/native.go

@@ -173,9 +173,7 @@ func DecodeBech32(addr crypto.Bech32Address) (prefix string, bytes [20]byte, ok
 	if err != nil || len(bz) != 20 {
 		return "", [20]byte{}, false
 	}
-	// TODO: can be simplified when we switch to go1.20 in go mod to be a simple [20]byte(bz)
-	copy(bytes[:], bz)
-	return prefix, bytes, true
+	return prefix, [20]byte(bz), true
 }
 
 func typedString(s gno.StringValue) gno.TypedValue {