message: Correct FSS and FBS snippets
  There are some typos in FSS and FBS snippets
diff: "description": "Use a bold font"
  },
  "textsuperscript": {
  - "pre": "FSS",
  - "body": "\\testsuperscript{${1:${TM_SELECTED_TEXT:text}}}",
  + "prefix": "FSS",
  + "body": "\\textsuperscript{${1:${TM_SELECTED_TEXT:text}}}",
  "description": "Make text a superscript"
  },
  "textsubscript": {
  - "pre": "FBS",
  - "body": "\\testsubscript{${1:${TM_SELECTED_TEXT:text}}}",
  + "prefix": "FBS",
  + "body": "\\textsubscript{${1:${TM_SELECTED_TEXT:text}}}",
  "description": "Make text a superscript"
  },
  "mathrm": {
  