Update required go

The go documentation says

  If the go command is not invoked with a -mod flag and the vendor directory
  is present and the "go" version in go.mod is 1.14 or higher, the go command
  will act as if it were invoked with -mod=vendor.

This updates go in go.mod so that the vendor directory is actually
used.

Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>

go.mod

@@ -1,6 +1,6 @@
 module github.com/scylladb/scylla-operator
 
-go 1.13
+go 1.14
 
 require (
 	github.com/bitly/go-hostpool v0.1.0 // indirect