[online-docs][4.1.5] 404 from link to properties

[space88man]

Describe the bug
The online docs 4.1.5 has a 404 link to properties:

https://docs.spring.io/spring-cloud-gateway/reference/spring-cloud-gateway/configuration-properties.html

The 404 link is
https://docs.spring.io/spring-cloud-gateway/reference/spring-cloud-gateway/appendix.html

[EeeasyCode]

@spencergibb

Hi, there!
I’ve created a PR to address this issue, and it includes a simple code fix! I would appreciate any feedback.

[spencergibb]

Closed via #3588