Step 1 – Backup phpMyAdmin

sudo mv /usr/share/phpmyadmin/ /usr/share/phpmyadmin.bak

Step 2 – Download Latest phpMyAdmin
  
sudo wget www.phpmyadmin.net/downloads/phpMyAdmin-latest-all-languages.zip
sudo mkdir /usr/share/phpmyadmin
unzip phpMyAdmin-latest-all-languages.zip -d /usr/share/phpmyadmin
  
Step 3 – Update Configuration

sudo nano /usr/share/phpmyadmin/libraries/vendor_config.php
  
and update the following values.
  
define('TEMP_DIR', '/var/lib/phpmyadmin/tmp/');
define('CONFIG_DIR', '/etc/phpmyadmin/');

credit : 

https://tecadmin.net/manually-upgrade-phpmyadmin-ubuntu/