fix deprecation warning in examples

Author: amancevice

examples/celery/compose.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   db:
     image: postgres

examples/mysql/compose.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   db:
     command: --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci

examples/postgres/compose.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   db:
     image: postgres

examples/sqlite/compose.yml

@@ -1,4 +1,3 @@
-version: '3'
 services:
   redis:
     image: redis