docs(prover): Recommend standard provisioning over spot (#2729)

## What ❔

A few reports have shown that using spot instances is very
luck-dependent, so it's not worth trying at the cost of flow disruption.

## Why ❔

<!-- Why are these changes done? What goal do they contribute to? What
are the principles behind them? -->
<!-- Example: PR templates ensure PR reviewers, observers, and future
iterators are in context about the evolution of repos. -->

## Checklist

<!-- Check your PR fulfills the following items. -->
<!-- For draft PRs check the boxes as you complete them. -->

- [ ] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [ ] Tests for the changes have been added / updated.
- [ ] Documentation comments have been added / updated.
- [ ] Code has been formatted via `zk fmt` and `zk lint`.

prover/docs/01_gcp_vm.md

@@ -31,9 +31,8 @@ When you choose the region, set the following options:
   - GPU Type: NVIDIA L4
   - Number of GPUs: 1
   - Machine type: Preset, `g2-standard-16`
-- Availability policies: Spot instances are much cheaper, but there is a chance that it will be preempted while you work
-  on it. If you're working on something that is not very important, spot instances are recommended. If any disruption
-  will be harmful, choose standard provisioning.
+- Availability policies: Choose standard provisioning. Spot instances can be preempted while you work on them, which
+  will disrupt your flow.
 - Then click on "VM provisioning model advanced settings" and
   - Click on "Set a time limit for the VM"
   - Set the limit to 8 hours