X-Xss-Protection header "1; mode=block" differs in Servlet and Reactive

[Kehrlann]

X-Xss-Protection header, when set to mode=block, is different in Servlet and Reactive stacks:

• X-Xss-Protection: 1; mode=block in Servlet
• X-Xss-Protection: 1 ; mode=block in Reactive, with an extra space

Is this something we want to address?

Discovered in issue: gh-9631