Remove Travis and Coverity badges from README.md

Summary

We are not using Travis. The "green" badge points to an old build with empty logs. Nobody takes care of Coverity. It has been failing for ages.

If we want fancy badges we need to take care of them.

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 %7.0.0

added patch label

added documentation label

mentioned in commit 51e15d69

merged