[time.cal.ymd.members] Fix misapplication of P1724R0: ld -> 1d.

Author: zygoloid

source/time.tex

@@ -6160,7 +6160,7 @@
 holding a count of days from the \tcode{sys_days} epoch to \tcode{*this}
 (a negative value if \tcode{*this} represents a date prior to the \tcode{sys_days} epoch).
 Otherwise, if \tcode{y_.ok() \&\& m_.ok()} is \tcode{true},
-returns \tcode{sys_days\{y_/m_/ld\} + (d_ - 1d)}.
+returns \tcode{sys_days\{y_/m_/1d\} + (d_ - 1d)}.
 Otherwise the value returned is unspecified.
 
 \pnum