prompt: update powerlevel10k submodule to the latest commit (#1757)

- New feature: Instant Prompt.
  - Zsh starts instantly even if zshrc loads dozens of plugins.
  - Must be explicitly enabled via `p10k configure`.
- New prompt segment: azure.
- New styles: Pure and Rainbow.
- 6 times faster loading (independent of instant prompt).

modules/prompt/external/powerlevel10k

@@ -1 +1 @@
-Subproject commit 5886154bb14965f59d26f349b97e2c5e9104bf93
+Subproject commit 4586e8d54c40fb6bd688128101ea5c853e34773b