improved tracks hover behavior (fix https://github.com/cBioPortal/cbioportal/issues/6021)
improved tracks hover behavior (fix https://github.com/cBioPortal/cbioportal/issues/6021)

Signed-off-by: Onur Sumer <s.onur.sumer@gmail.com>

Former-commit-id: ff67790d39a1a1c0258f2ebf100e41c7f4370998
alisman/cbioportal-frontend,alisman/cbioportal-frontend,cBioPortal/cbioportal-frontend,alisman/cbioportal-frontend,cBioPortal/cbioportal-frontend,alisman/cbioportal-frontend,alisman/cbioportal-frontend,cBioPortal/cbioportal-frontend,alisman/cbioportal-frontend,cBioPortal/cbioportal-frontend,cBioPortal/cbioportal-frontend,cBioPortal/cbioportal-frontend