message: Fix typo on multline environment
diff: "subequationsAst":{
  "text":"subequations*"
  },
  - "multiline":{
  - "text":"multiline"
  + "multline":{
  + "text":"multline"
  },
  - "multilineAst":{
  - "text":"multiline*"
  + "multlineAst":{
  + "text":"multline*"
  },
  "gather":{
  "text":"gather"
  