Simple XSS scans might fetch /<script>alert('vulnerable')</script>, and
fail when the response body includes the script tag verbatim, despite
the headers directing the browser to interpret the response as text.
This isn't a real vulnerability, but it's easier to fix this here than
it is to fix the scanners.
Kubernetes-commit: dd4bb1213d8447632fa651195980cbfae2546fb3