Remove some TODOs (#6488)

* Remove stale TODOs

* Ban TODO markers from markdown

* Scrub all TODOs from ci/ and book/

net/scripts/azure-provider.sh

@@ -126,7 +126,7 @@ cloud_Initialize() {
   declare networkName="$1"
   # ec2-provider.sh creates firewall rules programmatically, should do the same
   # here.
-  echo "TODO: create $networkName firewall rules programmatically instead of assuming the 'testnet' tag exists"
+  echo "Note: one day create $networkName firewall rules programmatically instead of assuming the 'testnet' tag exists"
 }
 
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