Update speech-synthesis-markup.md

Remove unsupported say-as tag "digit"

Author: ForrestGumb

articles/cognitive-services/Speech-Service/speech-synthesis-markup.md

@@ -768,7 +768,7 @@ The following content types are supported for the `interpret-as` and `format` at
 | `characters`, `spell-out` |  | The text is spoken as individual letters (spelled out). The speech synthesis engine pronounces:<br /><br />`<say-as interpret-as="characters">test</say-as>`<br /><br />As "T E S T." |
 | `cardinal`, `number` | None| The text is spoken as a cardinal number. The speech synthesis engine pronounces:<br /><br />`There are <say-as interpret-as="cardinal">10</say-as> options`<br /><br />As "There are ten options."|
 | `ordinal`  | None | The text is spoken as an ordinal number. The speech synthesis engine pronounces:<br /><br />`Select the <say-as interpret-as="ordinal">3rd</say-as> option`<br /><br />As "Select the third option."|
-| `digits`, `number_digit`  | None | The text is spoken as a sequence of individual digits. The speech synthesis engine pronounces:<br /><br />`<say-as interpret-as="number_digit">123456789</say-as>`<br /><br />As "1 2 3 4 5 6 7 8 9." |
+| `number_digit`  | None | The text is spoken as a sequence of individual digits. The speech synthesis engine pronounces:<br /><br />`<say-as interpret-as="number_digit">123456789</say-as>`<br /><br />As "1 2 3 4 5 6 7 8 9." |
 | `fraction`   | None | The text is spoken as a fractional number. The speech synthesis engine pronounces:<br /><br /> `<say-as interpret-as="fraction">3/8</say-as> of an inch`<br /><br />As "three eighths of an inch."  |
 | `date` | dmy, mdy, ymd, ydm, ym, my, md, dm, d, m, y | The text is spoken as a date. The `format` attribute specifies the date's format (*d=day, m=month, and y=year*). The speech synthesis engine pronounces:<br /><br />`Today is <say-as interpret-as="date" format="mdy">10-19-2016</say-as>`<br /><br />As "Today is October nineteenth two thousand sixteen." |
 | `time`  | hms12, hms24  | The text is spoken as a time. The `format` attribute specifies whether the time is specified by using a 12-hour clock (hms12) or a 24-hour clock (hms24). Use a colon to separate numbers representing hours, minutes, and seconds. Here are some valid time examples: 12:35, 1:14:32, 08:15, and 02:50:45. The speech synthesis engine pronounces:<br /><br />`The train departs at <say-as interpret-as="time" format="hms12">4:00am</say-as>`<br /><br />As "The train departs at four A M." |