parser bug on docs with double backticks

[stew]

Input:

```unison:hide
x = {{
    ``let "me"`` live
    ``do "me"`` in      
  }}
```

Output:

  I got confused here:
  
      2 |     ``let "me"`` live
  
  
  I was surprised to find a syntax.docWord here.
  I was expecting one of these instead:
  
  * :
  * and
  * bang
  * do
  * false
  * handle
  * if
  * infixApp
  * let
  * or
  * quote
  * termLink
  * true
  * tuple
  * typeLink

This is causing a round trip error with our website currently for this term:

https://share.unison-lang.org/@unison/website/code/main/latest/terms/learn/languageReference/delayedComputations/syntacticPrecedence