Use more explicit grep (thanks to @MichaIng)

Signed-off-by: ChillerDragon <ChillerDragon@gmail.com>

automated install/basic-install.sh

@@ -188,7 +188,7 @@ os_check() {
         local remote_os_domain valid_os valid_version valid_response detected_os detected_version display_warning cmdResult digReturnCode response
         remote_os_domain="versions.pi-hole.net"
 
-        detected_os=$(grep "\\bID\\b" /etc/os-release | cut -d '=' -f2 | tr -d '"')
+        detected_os=$(grep '^ID=' /etc/os-release | cut -d '=' -f2 | tr -d '"')
         detected_version=$(grep VERSION_ID /etc/os-release | cut -d '=' -f2 | tr -d '"')
 
         cmdResult="$(dig +short -t txt ${remote_os_domain} @ns1.pi-hole.net 2>&1; echo $?)"