Proactively bump golang.org/x/net to v0.12.0

Proactively bump to v0.12.0 to avoid v0.10.0 and v0.11.0, which contain
a regression added by commit
82780d606d.
This commit was later reverted in v0.12.0.

Generated with:

hack/pin-dependency.sh golang.org/x/net v0.12.0 && hack/update-vendor.sh

vendor/golang.org/x/text/unicode/bidi/tables13.0.0.go

@@ -1,7 +1,7 @@
 // Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
-//go:build go1.16
-// +build go1.16
+//go:build go1.16 && !go1.21
+// +build go1.16,!go1.21
 
 package bidi
 

vendor/golang.org/x/text/unicode/norm/tables13.0.0.go

@@ -1,7 +1,7 @@
 // Code generated by running "go generate" in golang.org/x/text. DO NOT EDIT.
 
-//go:build go1.16
-// +build go1.16
+//go:build go1.16 && !go1.21
+// +build go1.16,!go1.21
 
 package norm