build: move away from latest tag for dependabot

Author: erik-perri

docker/data-source-services/docker-compose.yml

@@ -7,7 +7,7 @@ services:
   nginxproxy:
 # Enable nginx debug and increase output verbosity
 #    command: [nginx-debug, '-g', 'daemon off;']
-    image: jwilder/nginx-proxy
+    image: jwilder/nginx-proxy:1.9
     container_name: sourcetoad_nginx_proxy
     ports:
       - "80:80"

docker/data-source-tools/docker-compose.yml

@@ -1,7 +1,7 @@
 ---
 services:
   mailpit:
-    image: axllent/mailpit:latest
+    image: axllent/mailpit:1.28
     container_name: sourcetoad_mailpit
     ports:
       - "8025:8025"
@@ -28,7 +28,7 @@ services:
     networks:
       - st-internal
   phpmyadmin:
-    image: phpmyadmin/phpmyadmin:latest
+    image: phpmyadmin/phpmyadmin:5.2
     container_name: sourcetoad_phpmyadmin
     ports:
       - "8080:80"