Update GasStripping test
After implementing src#684 (closed), GAS attribute has been moved from OpalVacuum to ParticleMatterInteracion. Then, GasStripping test must be updated
Code indexing in gitaly is broken and leads to code not being visible to the user. We work on the issue with highest priority.
After implementing src#684 (closed), GAS attribute has been moved from OpalVacuum to ParticleMatterInteracion. Then, GasStripping test must be updated