Fix antora build warnings

modules/ROOT/pages/kernel/build-custom-kernel.adoc

@@ -70,10 +70,10 @@ to check out that branch with:
 1. Check out the branch for which you would like to build a kernel (`master`
 corresponds to Rawhide):
 
-[source,bash]
-----
-git checkout origin/f28
-----
+    [source,bash]
+    ----
+    git checkout origin/f28
+    ----
 
 2. To avoid conflicts with existing kernels, you can set a custom buildid by
 changing `# define buildid .local` to `%define buildid .<your_custom_id_here>`
@@ -83,17 +83,17 @@ in `kernel.spec`.
 
 4. Build the RPMs:
 
-[source,bash]
-----
-fedpkg local
-----
+    [source,bash]
+    ----
+    fedpkg local
+    ----
 
 5. Install the new kernel:
 
-[source,bash]
-----
-sudo dnf install --nogpgcheck ./x86_64/kernel-$version.rpm
-----
+    [source,bash]
+    ----
+    sudo dnf install --nogpgcheck ./x86_64/kernel-$version.rpm
+    ----
 
 
 === Building a non-debugging kernel