cerbero: Fix bundle-source command

It was missing an --offline flag, to match build and package.
7 jobs for fix-bundlesource in 64 minutes and 23 seconds
Status Name Job ID Coverage
  Preparation
passed manifest #85792

00:00:41

 
  Build
passed cerbero deps fedora x86_64 #85793

00:47:52

passed cerbero deps windows x86 #85794

00:45:09

passed cerbero deps windows x86_64 #85795

00:45:39

 
  Full Builds
passed build cerbero cross win32 #85797

00:15:49

passed build cerbero cross win64 #85798

00:12:41

passed build cerbero fedora x86_64 #85796

00:13:22