Fractional seconds are not captured

[billdenney]

library(parsedate)
# positive hour timezone with minutes and fractional seconds
dput(
  parse_iso_8601("2024-08-03T01:02:03.123+04:15")
)
#> structure(1722631623, class = c("POSIXct", "POSIXt"), tzone = "UTC")
# fractional seconds are not captured
dput(
  as.POSIXct("2024-08-03 01:02:03.123")
)
#> structure(1722661323.123, class = c("POSIXct", "POSIXt"), tzone = "")

^{Created on 2024-08-03 with reprex v2.1.1}

[billdenney]

This was an issue that I caused during other changes. It is not an issue, but I'm leaving a test for it because I don't think it's specifically tested elsewhere.

[billdenney]

... And, it turns out that this is an issue after all, but it is masked by r-lib/testthat#1977.