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"
 }
 
 #

net/scripts/disable-background-upgrades.sh

@@ -3,8 +3,8 @@ set -ex
 #
 # Prevent background upgrades that block |apt-get|
 #
-# TODO: This approach is pretty uncompromising.  An alternative solution that
-#       doesn't involve deleting system files would be welcome.
+# This approach is pretty uncompromising.  An alternative solution that doesn't
+# involve deleting system files would be welcome.
 
 [[ $(uname) = Linux ]] || exit 1
 [[ $USER = root ]] || exit 1

net/scripts/gce-provider.sh

@@ -122,7 +122,7 @@ 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"
 }
 
 #
@@ -170,8 +170,8 @@ cloud_CreateInstances() {
   if $enableGpu; then
     # Custom Ubuntu 18.04 LTS image with CUDA 9.2 and CUDA 10.0 installed
     #
-    # TODO: Unfortunately this image is not public.  When this becomes an issue,
-    # use the stock Ubuntu 18.04 image and programmatically install CUDA after the
+    # Unfortunately this image is not public.  When this becomes an issue, use
+    # the stock Ubuntu 18.04 image and programmatically install CUDA after the
     # instance boots
     #
     imageName="ubuntu-1804-bionic-v20181029-with-cuda-10-and-cuda-9-2"