remove spurious "toolchain" from go.mod (#819)

Having go.mod specific a exact toolchain is not required and breaks
some build systems.  The preference is to remove this allow Go to use
the appropriate installed tooling.

Author: cwedgwood

go.mod

@@ -2,8 +2,6 @@ module github.com/onsi/gomega
 
 go 1.22.0
 
-toolchain go1.22.10
-
 require (
 	github.com/google/go-cmp v0.6.0
 	github.com/onsi/ginkgo/v2 v2.22.2