docs: convert alerts to use GitHub Flavored Markdown (GFM) (#16850)

followup to #16761 

thanks @lucasmelin !

+ thanks: @ethanndickson @Parkreiner @matifali @aqandrew 

- [x] update snippet
- [x] find/replace
- [x] spot-check


[preview](https://coder.com/docs/@16761-gfm-callouts/admin/templates/managing-templates/schedule)
(and others)

---------

Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com>
Co-authored-by: M Atif Ali <atif@coder.com>

docs/start/local-deploy.md

@@ -15,8 +15,7 @@ simplicity.
 
 First, install [Docker](https://docs.docker.com/engine/install/) locally.
 
-> If you already have the Coder binary installed, restart it after installing
-> Docker.
+If you already have the Coder binary installed, restart it after installing Docker.
 
 <div class="tabs">
 
@@ -30,7 +29,8 @@ curl -L https://coder.com/install.sh | sh
 
 ## Windows
 
-> **Important:** If you plan to use the built-in PostgreSQL database, you will
+> [!IMPORTANT]
+> If you plan to use the built-in PostgreSQL database, you will
 > need to ensure that the
 > [Visual C++ Runtime](https://learn.microsoft.com/en-US/cpp/windows/latest-supported-vc-redist#latest-microsoft-visual-c-redistributable-version)
 > is installed.