fix broken links for docs/getting-started/quickstart-install/ page (#6487) (#6488)

* fix broken links for production YAML and Operator installation docs

* remove direct .md file references

* try this

Co-authored-by: Gregg Ellis Schofield <[email protected]>

Author: dprotaso

docs/snippets/quickstart-prereqs.md

@@ -6,8 +6,8 @@
 
 !!! warning
     Knative `quickstart` environments are for experimentation use only.
-    For a production ready installation, see the [YAML-based installation](/docs/install/yaml-install/)
-    or the [Knative Operator installation](/docs/install/operator/knative-with-operators/).
+    For a production ready installation, see the [YAML-based installation](../install/yaml-install/README.md)
+    or the [Knative Operator installation](../install/operator/knative-with-operators.md).
 
 Before you can get started with a Knative `quickstart` deployment you must install: