Fix deprecated container config

Context: https://stackoverflow.com/questions/55987337/visual-studio-code-remote-containers-change-shell#comment121528642_65972905

.devcontainer/devcontainer.json

@@ -5,7 +5,7 @@
     },
     // Set *default* container specific settings.json values on container create.
     "settings": {
-        "terminal.integrated.shell.linux": "/bin/bash"
+        "terminal.integrated.defaultProfile.linux": "bash"
     },
     // Add the IDs of extensions you want installed when the container is created.
     // Browse for extensions here: https://marketplace.visualstudio.com/