Editorial: Collapse nonterminals only used for disambiguation

[ptomato]

Prefer language like "the first |TemporalDecimalFraction|, if present" rather than defining several nonterminals such as |TimeFraction|, |DurationHoursFraction|, etc.

Closes: #2006

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (7bd3589) 96.59% compared to head (d9d1722) 96.57%.
Report is 2 commits behind head on main.

Files	Patch %	Lines
polyfill/lib/ecmascript.mjs	95.34%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2767      +/-   ##
==========================================
- Coverage   96.59%   96.57%   -0.02%     
==========================================
  Files          23       23              
  Lines       12218    12243      +25     
  Branches     2263     2268       +5     
==========================================
+ Hits        11802    11824      +22     
- Misses        356      358       +2     
- Partials       60       61       +1     

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