Hiding the dashed line in a text crescendo

Text crescendi (or decrescendi, ritardandi, etc.) show a dashed line by default. To hide this spanner line, simply set the dash-period of DynamicTextSpanner (or TextSpanner if you use one for “rit.”) to a negative value.

\version "2.24.0"

%% http://lsr.di.unimi.it/LSR/Item?id=404

\relative c'' {
  % Default: Dashed line
  \crescTextCresc 
  c4\< c c c\!
  \crescTextCresc 
  \once \override DynamicTextSpanner.style = #'none
  c4\< c c c\!
}