Make Qt ActiveQt examples self-contained

The comapp, simple, and wrapper examples included a sibling shared.pri
that suppressed the ActiveX server registration post-link step when the
JENKINS_HOME environment variable was set. Qt CI stopped using Jenkins
years ago, so the file has been a no-op ever since.

Including a file from a sibling directory also violates QUIP-13 and
prevents Qt Creator and the VS Code extension from copying an example
out of the example tree.

Remove the shared.pri include from the three examples and delete the
file. Each example now builds standalone from its own directory.

Pick-to: 6.11 6.12
Fixes: QTBUG-147525
Change-Id: I455f396272ac293cea7dab5e1e9d78c98a7d321c
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>