Remove unused Si Detector Element Collection

as the title says, we are not using it

This merge request affects 2 packages:

• Tracking/Acts/ActsConfig
• Tracking/Acts/ActsDataPreparation

Affected files list will not be printed in this case

Adding @tbold ,@cvarni ,@pagessin ,@jojungge ,@adye ,@toyamaza as watchers

added ACTS Tracking main review-pending-level-1 labels

CI Result SUCCESS (hash b30f9738)

	Athena
externals
cmake
make
tests

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Athena: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-EL9 5598] (remote access info)

Looks good to me. L1

added review-approved label and removed review-pending-level-1 label

mentioned in commit c7d42b7a

merged