Remove DownloadSRTMTiles

Summary

The DownloadSRTMTiles has been deprecated in OTB 7.3 because the download link is broken (downloading these tiles now require authentication, which is not super compatible with the API of this application).

This merge request removes the application for OTB 8.0.

It also update the documentation of the elevation parameter, which was mentioning the application.

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.

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Check before merging:

• All discussions are resolved
• At least 2 votes from core developers, no vote.
• The feature branch is (reasonably) up-to-date with the base branch
• Dashboard is green
• Copyright owner has signed the ORFEO ToolBox Contributor License Agreement
• Optionally, run git diff develop... -U0 --no-color | clang-format-diff.py -p1 -i on latest changes and commit

changed milestone to %8.0.0

added documentation refactoring labels

assigned to @ctraizet

merged

mentioned in commit 167b1733

mentioned in issue #2164 (closed)