docs: Remove pre-release markers

Author: Danielku15

docs/alphatex/percussion.mdx

@@ -1,11 +1,11 @@
 ---
 title: Percussion
-since: 1.4.0-alpha.1026
+since: 1.4.0
 ---
 
 import { SinceBadge } from '@site/src/components/SinceBadge';
 
-<SinceBadge since="1.4.0-alpha.1026" />
+<SinceBadge since="1.4.0" />
 
 import { AlphaTexSample } from '@site/src/components/AlphaTexSample';
 

docs/guides/exporter.mdx

@@ -12,11 +12,7 @@ import { SinceBadge } from '@site/src/components/SinceBadge';
 After alphaTab has loaded a full [`Score`](/docs/reference/score) object from any input source, it can also be exported again to one of the supported export formats. 
 Supported export formats: 
 
-- Guitar Pro 7 (alphaTab.exporter.Gp7Exporter) <span className="badge badge--info">since 1.2.0-alpha.75</span>
-
-:::note
-More exporters are planned for the 1.5 release unless special feature requests of users are incoming. 
-:::
+- Guitar Pro 7 (alphaTab.exporter.Gp7Exporter) <span className="badge badge--info">since 1.2.0</span>
 
 To export a `Score` object the corresponding exporter needs to be created and called. Then the resulting binary array can be used further to 
 trigger a download, send it to a server, save it to a file etc. 

docs/showcase/special-tracks.mdx

@@ -13,7 +13,7 @@ percussion track, it's hidden in case a drum tab is displayed.
 With Guitar Pro 6 files also grand staffs can be rendered.
 <AlphaTab file="/files/features/Piano.gpx" />
 
-## Percussion <span class="badge badge--info badge--header">since 1.1.0-alpha.45</span>
+## Percussion <span class="badge badge--info badge--header">since 1.1.0</span>
 
 Percussion tracks are similar to drum tabs but might have less lines than a normal staff. 
 <AlphaTab file="/files/features/Percussion.gp" tracks="all" />