Simplify one-pager placeholder text

Point straight at PR vmware-tanzu#1893 without explaining why the file was
split out.

Author: aruneshpa

external/kubevm/docs/one-pager-kubevm-generic-api.md

@@ -2,7 +2,6 @@
 
 **Author:** Arunesh Pandey · **Status:** Proposal, open for discussion
 
-This proposal is under active review as a pull request rather than as a
-single large file, so that reviewers can comment inline on specific
-sections. See [#1893](https://github.com/vmware-tanzu/vm-operator/pull/1893)
-for the current content and discussion.
+This proposal is under review. Go to
+[#1893](https://github.com/vmware-tanzu/vm-operator/pull/1893) to read it
+and leave comments/feedback.