Fix several errors that continue to block successful builds of the downstream docs :

• notification.adoc: Content in table fails to render downstream. Fix callouts
• db2.adoc: L 311: Fix target id in internal xref
• mysql.adoc: L730, Update target ID in xref
• shared ad hoc snapshots file (/partials/con-connector-ad-hoc-snapshots.adoc). Some content fails to render downstream:
  • L 87-108 Remove commented content that was moved to separate shared file.
  • L96: Fix formatting of xref