chore: lower go version requirement to 1.21

OpenClaw · OpenClaw · commit 22f28e45696a · 2026-03-10T07:51:19.000+08:00
diff --git a/go.mod b/go.mod
@@ -1,3 +1,3 @@
 module github.com/devfeel/mapper
 
-go 1.22.2
+go 1.21

Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,3 @@`
`1`	`1`	`module github.com/devfeel/mapper`
`2`	`2`
`3`		`-go 1.22.2`
	`3`	`+go 1.21`