Because using "+" signs for newlines is not part of the R syntax, those are just an artifact from the console, the correct way of writing it on a script is this one
tripdata_202006 <- read_csv("Bike data/202006-divvy-tripdata.csv",
col_types = cols(started_at = col_datetime(format = "%m/%d/%Y %H:%M"),
ended_at = col_datetime(format = "%m/%d/%Y %H:%M"),
start_station_id = col_character(),
end_station_id = col_character())
)