apollo@2.31.0: Release

 - apollo-codegen-core@0.38.0
 - apollo-codegen-flow@0.36.0
 - apollo-codegen-scala@0.37.0
 - apollo-codegen-swift@0.38.0
 - apollo-codegen-typescript@0.38.0
 - apollo-language-server@1.24.0
 - apollo@2.31.0
 - vscode-apollo@1.17.0