fix escaping literal

Author: whoiskatrin

src/content/docs/sandbox/index.mdx

@@ -121,13 +121,14 @@ df['sales'].sum()  # Last expression is automatically returned
     			const sandbox = getSandbox(env.Sandbox, 'user-123');
 
     			// Start a WebSocket echo server
-    			await sandbox.writeFile('/workspace/server.js', \`
+    			const serverCode = `
     				Bun.serve({
     					port: 8080,
     					fetch(req, server) { if (server.upgrade(req)) return; },
-    					websocket: { message(ws, msg) { ws.send(\\\`Echo: \${msg}\\\`); } }
+    					websocket: { message(ws, msg) { ws.send(\`Echo: \${msg}\`); } }
     				});
-    			\`);
+    			`;
+    			await sandbox.writeFile('/workspace/server.js', serverCode);
     			await sandbox.startProcess('bun /workspace/server.js');
 
     			// Route WebSocket connections to the server