docs: Bump Atlantis version (#96)

Author: vdmgolub

README.md

@@ -17,8 +17,8 @@ Since Atlantis does not have a plugins concept, you need to decide which deploym
 
 #### a. Use our Docker images (recommended)
 Use our [`infracost-atlantis`](https://hub.docker.com/r/infracost/infracost-atlantis) Docker images that [extend](https://www.runatlantis.io/docs/deployment.html#customization) the Atlantis image to add Infracost. We maintain tags for the latest two 0.x versions of Atlantis:
+  - `infracost/infracost-atlantis:atlantis0.31-infracost0.10` latest patch version of Atlantis v0.31 and Infracost v0.10
   - `infracost/infracost-atlantis:atlantis0.30-infracost0.10` latest patch version of Atlantis v0.30 and Infracost v0.10
-  - `infracost/infracost-atlantis:atlantis0.29-infracost0.10` latest patch version of Atlantis v0.29 and Infracost v0.10
   - `infracost/infracost-atlantis:latest` latest versions of Atlantis and Infracost
 
 #### b. Build your own Docker image