chore(na): update app dev to use python3 (#1748)

* chore(na): update app dev to use python3

* bump dev couchdb to v 3.4.2

* reverting couch2 upgrade - still needed for cht 3.x - sorry!

content/en/contribute/code/core/dev-environment.md

@@ -30,7 +30,7 @@ _(Node {{< param nodeVersion >}} is the environment used to run the CHT server i
 {{< tabpane persist=false lang=shell >}}
 {{< tab header="Linux (Ubuntu)" >}}
 sudo apt update && sudo apt -y dist-upgrade
-sudo apt -y install xsltproc curl uidmap jq python2 git make g++
+sudo apt -y install xsltproc curl uidmap jq python3 git make g++
 # Use NVM to install NodeJS:
 export nvm_version=`curl -s https://api.github.com/repos/nvm-sh/nvm/releases/latest | jq -r .name`
 curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/$nvm_version/install.sh | $SHELL