chore: remove gm from block times guide

guides/block-times.md

@@ -1,6 +1,6 @@
 # How to change speed of block production
 
-If you have gone through both the [GM world](./gm-world) and the
+If you have gone through both the [quick start tutorial](../tutorials/quick-start.md) and the
 [Full and sequencer node rollup setup](./full-and-sequencer-node)
 already, you're now ready to experiment with faster block times.