MM-43753: Go mod tidy for 1.18 (#20073)

We bump the go.mod version to 1.18
and run go mod tidy.

This is required for using new features.

```release-note
NONE
```

vendor/github.com/gorilla/handlers/go.mod

@@ -1,5 +0,0 @@
-module github.com/gorilla/handlers
-
-go 1.14
-
-require github.com/felixge/httpsnoop v1.0.1

vendor/github.com/gorilla/handlers/go.sum

@@ -1,2 +0,0 @@
-github.com/felixge/httpsnoop v1.0.1 h1:lvB5Jl89CsZtGIWuTcDM1E/vkVs49/Ml7JJe07l8SPQ=
-github.com/felixge/httpsnoop v1.0.1/go.mod h1:m8KPJKqk1gH5J9DgRY2ASl2lWCfGKXixSwevea8zH2U=

vendor/github.com/gorilla/mux/go.mod

@@ -1,3 +0,0 @@
-module github.com/gorilla/mux
-
-go 1.12

vendor/github.com/gorilla/websocket/go.mod

@@ -1,3 +0,0 @@
-module github.com/gorilla/websocket
-
-go 1.12