[ruby mode] Require dash or tilde at start of heredoc strings
[ruby mode] Require dash or tilde at start of heredoc strings

Closes #5871

pabloferz/CodeMirror,dperetti/CodeMirror,mtaran-google/CodeMirror,pabloferz/CodeMirror,mtaran-google/CodeMirror,hackmdio/CodeMirror,wingify/CodeMirror,codio/CodeMirror,notepadqq/CodeMirror,wingify/CodeMirror,dperetti/CodeMirror,hackmdio/CodeMirror,notepadqq/CodeMirror,nightwing/CodeMirror,nightwing/CodeMirror,codio/CodeMirror,thomasjm/CodeMirror,thomasjm/CodeMirror,dperetti/CodeMirror,notepadqq/CodeMirror,codio/CodeMirror,nightwing/CodeMirror,hackmdio/CodeMirror,wingify/CodeMirror,thomasjm/CodeMirror,pabloferz/CodeMirror,mtaran-google/CodeMirror