Update "Upgrade from Gogs" en-us doc

- Move "Change gogs specific information" FROM/TO steps up
  to just beneath matching section header, adjust indention
  and explicitly specify syntax of code sample to provide
  highlighting

- Adjust header levels to match what appears to be the
  intended level, remove trailing decoration (see below)

- Move "Upgrading to most recent ..." section down, remove
  decoration (section header formatting likely covers this
  well enough already)

refs go-gitea#4286, go-gitea#3558

Author: deoren

docs/content/doc/upgrade/from-gogs.en-us.md

@@ -33,50 +33,53 @@ There are some basic steps to follow. On a Linux system run as the Gogs user:
 * Enter Gitea admin panel on the UI, run `Rewrite '.ssh/authorized_keys' file`.
 * If custom or config path was changed, run `Rewrite all update hook of repositories`.
 
-### Change gogs specific information:
+## Change gogs specific information
 
 * Rename `gogs-repositories/` to `gitea-repositories/`
 * Rename `gogs-data/` to `gitea-data/`
 * In `gitea/custom/conf/app.ini` change:
 
-### Upgrading to most recent `gitea` version:
+  FROM:
+
+  ```ini
+  [database]
+  PATH = /home/:USER/gogs/data/:DATABASE.db
+  [attachment]
+  PATH = /home/:USER/gogs-data/attachments
+  [picture]
+  AVATAR_UPLOAD_PATH = /home/:USER/gogs-data/avatars
+  [log]
+  ROOT_PATH = /home/:USER/gogs/log
+  ```
+
+  TO:
+
+  ```ini
+  [database]
+  PATH = /home/:USER/gitea/data/:DATABASE.db
+  [attachment]
+  PATH = /home/:USER/gitea-data/attachments
+  [picture]
+  AVATAR_UPLOAD_PATH = /home/:USER/gitea-data/avatars
+  [log]
+  ROOT_PATH = /home/:USER/gitea/log
+  ```
+
+* Verify by starting Gitea with `gitea web`
+
+## Upgrading to most recent `gitea` version
+
 After successful migration from `gogs` to `gitea 1.0.x` it is possible to upgrade to the recent `gitea` version.
 Simply download the file matching the destination platform from the [downloads page](https://dl.gitea.io/gitea)
 and replace the binary.
 
-FROM:
-```
-[database]
-PATH = /home/:USER/gogs/data/:DATABASE.db
-[attachment]
-PATH = /home/:USER/gogs-data/attachments
-[picture]
-AVATAR_UPLOAD_PATH = /home/:USER/gogs-data/avatars
-[log]
-ROOT_PATH = /home/:USER/gogs/log
-```
-
-TO:
-```
-[database]
-PATH = /home/:USER/gitea/data/:DATABASE.db
-[attachment]
-PATH = /home/:USER/gitea-data/attachments
-[picture]
-AVATAR_UPLOAD_PATH = /home/:USER/gitea-data/avatars
-[log]
-ROOT_PATH = /home/:USER/gitea/log
-```
-
-* Verify by starting Gitea with `gitea web`
-
-### Troubleshooting
+## Troubleshooting
 
 * If errors are encountered relating to custom templates in the `gitea/custom/templates`
   folder, try moving the templates causing the errors away one by one. They may not be
   compatible with Gitea or an update.
 
-### Add Gitea to startup on Unix
+## Add Gitea to startup on Unix
 
 Update the appropriate file from [gitea/contrib](https://github.com/go-gitea/gitea/tree/master/contrib)
 with the right environment variables.