chore(deps): update dependency go to v1.23.6 (#69)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

go.mod

@@ -2,7 +2,7 @@ module github.com/moov-io/signedxml
 
 go 1.21.0
 
-toolchain go1.23.5
+toolchain go1.23.6
 
 require (
 	github.com/beevik/etree v1.5.0