release: update backport versions for 1.10.0 (#25595)

With the release of Nomad 1.10.0-rc.1, we'll start backporting to the 1.10.x
release series. Add this to the supported versions and remove 1.7.x.

Author: tgross

.release/versions.hcl

@@ -6,14 +6,15 @@
 
 schema = 1
 active_versions {
-  version "1.9.x" {
+  version "1.10.x" {
     ce_active = true
+    lts       = true
+  }
+  version "1.9.x" {
+    ce_active = true # needed for docs
   }
   version "1.8.x" {
-    ce_active = true
+    ce_active = true # needed for docs
     lts       = true
   }
-  version "1.7.x" {
-    ce_active = true
-  }
 }