[doc] fixing regex in example of rewrite
[doc] fixing regex in example of rewrite

avoids /somethingfoo to be matched by regex

Signed-off-by: Marcos Estevez <94f4c3b5670698e0b6a6aad56e6677d9ac95b503@gmail.com>

aledbf/ingress-nginx,kubernetes/ingress-nginx,canhnt/ingress,kubernetes/ingress-nginx,caicloud/ingress,canhnt/ingress,aledbf/ingress-nginx,kubernetes/ingress-nginx,canhnt/ingress,kubernetes/ingress-nginx,caicloud/ingress,caicloud/ingress,canhnt/ingress,kubernetes/ingress-nginx,aledbf/ingress-nginx,caicloud/ingress,aledbf/ingress-nginx