Removes problematic README links that point to nonexistent files

These prevent terragrunt applies.

prod/aws-us-gov/mdr-prod-c2/090-instance-teleport/README.md

@@ -1 +0,0 @@
-../../../../test/aws-us-gov/mdr-test-c2/090-instance-teleport/README.md

test/aws-us-gov/mdr-test-c2/090-instance-vault/README.md

@@ -1 +0,0 @@
-../../../../prod/aws-us-gov/mdr-prod-c2/090-instance-vault/README.md