Update install script to check for python 3.9

new raspbian has python set to 3.9.2

Author: DomAmato

install.sh

@@ -13,7 +13,7 @@ set -euo pipefail
 # This script will install the Hologram SDK and the necessary software dependencies
 # for it to work.
 
-required_programs=('python3' 'pip3' 'ps' 'kill' 'libpython3.7-dev')
+required_programs=('python3' 'pip3' 'ps' 'kill' 'libpython3.9-dev')
 OS=''
 
 # Check OS.