Update release-1.7 for version changes in 1.9 (#6520)

* Update version numbers to include 1.9

🛑 DO NOT MERGE 🛑

Update config files to use 1.9 as version number.

* Update _config.yml

_config.yml

@@ -23,11 +23,16 @@ defaults:
       githubbranch: "v1.7.3"
       docsbranch: "release-1.7"
       versions:
-        - fullversion: "v1.8.0"
+        - fullversion: "v1.9.0"
-          version: "v1.8"
+          version: "v1.9"
-          githubbranch: "v1.8.0"
+          githubbranch: "v1.9.0"
-          docsbranch: "release-1.8"
+          docsbranch: "release-1.9"
           url: https://kubernetes.io/docs/home/
+        - fullversion: "v1.8.4"
+          version: "v1.8"
+          githubbranch: "v1.8.4"
+          docsbranch: "release-1.8"
+          url: https://v1-8.docs.kubernetes.io/docs/home/
         - fullversion: "v1.7.3"
           version: "v1.7"
           githubbranch: "v1.7.3"
@@ -43,11 +48,6 @@ defaults:
           githubbranch: "v1.5.7"
           docsbranch: "release-1.5"
           url: https://v1-5.docs.kubernetes.io/docs/
-        - fullversion: "v1.4.12"
-          version: "v1.4"
-          githubbranch: "v1.4.12"
-          docsbranch: "release-1.4"
-          url: https://v1-4.docs.kubernetes.io/docs/
       deprecated: true
       currentUrl: https://kubernetes.io/docs/home/
       nextUrl: http://kubernetes-io-vnext-staging.netlify.com/