unbreak formating

Author: adrianschroeter

docs/source_assets.adoc

@@ -54,12 +54,12 @@ Remote assets that will be downloaded before the build can be added via the
 comment `#!RemoteAssetUrl: https://my.url/asset.tar`. `pbuild` will fetch the
 asset before the build and will make it available in the buildroot so that the
 asset can copied into the container as follows:
-[source,Dockerfile]
-----
-#!RemoteAssetUrl: https://my.url/asset.tar
-COPY asset.tar .
-RUN tar -xvzf asset.tar
-----
+
+  ----
+  #!RemoteAssetUrl: https://my.url/asset.tar
+  COPY asset.tar .
+  RUN tar -xvzf asset.tar
+  ----
 
 ==== Arch Linux PKGBUILD