docs: Add a missing "," in the C/C++ debugger configuration (#35098)

Release Notes:

- N/A

docs/src/languages/cpp.md

@@ -127,7 +127,7 @@ You can use CodeLLDB or GDB to debug native binaries. (Make sure that your build
       "command": "make",
       "args": ["-j8"],
       "cwd": "$ZED_WORKTREE_ROOT"
-    }
+    },
     "program": "$ZED_WORKTREE_ROOT/build/prog",
     "request": "launch",
     "adapter": "CodeLLDB"