Add string fo 4.0

Author: Smolevich

.github/workflows/build-ci.yml

@@ -15,15 +15,15 @@ jobs:
       matrix:
         include:
         - { os: ubuntu-latest, php: 7.2, mongodb: 3.6, experimental: true}
-        - { os: ubuntu-latest, php: 7.2, mongodb: 4.0, experimental: true}
+        - { os: ubuntu-latest, php: 7.2, mongodb: '4.0', experimental: true}
         - { os: ubuntu-latest, php: 7.2, mongodb: 4.2, experimental: true}
         - { os: ubuntu-latest, php: 7.2, mongodb: 4.4, experimental: true}
         - { os: ubuntu-latest, php: 7.3, mongodb: 3.6, experimental: false}
-        - { os: ubuntu-latest, php: 7.3, mongodb: 4.0, experimental: false}
+        - { os: ubuntu-latest, php: 7.3, mongodb: '4.0', experimental: false}
         - { os: ubuntu-latest, php: 7.3, mongodb: 4.2, experimental: false}
         - { os: ubuntu-latest, php: 7.3, mongodb: 4.4, experimental: false}
         - { os: ubuntu-latest, php: 7.4, mongodb: 3.6, experimental: false}
-        - { os: ubuntu-latest, php: 7.4, mongodb: 4.0, experimental: false}
+        - { os: ubuntu-latest, php: 7.4, mongodb: '4.0', experimental: false}
         - { os: ubuntu-latest, php: 7.4, mongodb: 4.2, experimental: false}
         - { os: ubuntu-latest, php: 7.4, mongodb: 4.4, experimental: false}
     services: