Update dev container setup

- Use /workspace/sentry-ruby as appearently it's needed for specs to pass
- Set Ruby version manager to "none" for Ruby LSP because it doesn't figure it out by itself

.devcontainer/devcontainer.json

@@ -2,13 +2,17 @@
   "name": "sentry-ruby",
   "dockerComposeFile": "docker-compose.yml",
   "service": "app",
-  "workspaceFolder": "/workspace/sentry",
+  "workspaceFolder": "/workspace/sentry-ruby",
   "customizations": {
     "vscode": {
       "extensions": [
         "sleistner.vscode-fileutils",
         "Shopify.ruby-lsp"
-      ]
+      ],
+      "settings": {}
+    },
+    "rubyLsp.rubyVersionManager": {
+      "identifier": "none"
     }
   },
   "remoteUser": "sentry",

.devcontainer/docker-compose.yml

@@ -7,7 +7,7 @@ services:
         IMAGE: ${IMAGE}
         TAG: ${TAG}
     volumes:
-      - ..:/workspace/sentry:cached
+      - ..:/workspace/sentry-ruby:cached
     command: sleep infinity
     environment:
       - REDIS_URL=${REDIS_URL:-redis://redis:6379/0}