Remove - and : from example DTSTAMPs

Remove - and : from example DTSTAMPs

RFC 5545 does not use these separators (unfortunately) in their dates
and times.  See sections 3.3.4 (Date), 3.3.5 (Date-Time), and 3.3.12
(Time), which specify:

  date               = date-value
  date-value         = date-fullyear date-month date-mday
  date-fullyear      = 4DIGIT
  date-month         = 2DIGIT        ;01-12
  date-mday          = 2DIGIT        ;01-28, 01-29, 01-30, 01-31
                                     ;based on month/year

  date-time  = date "T" time ;As specified in the DATE and TIME
                             ;value definitions

  time         = time-hour time-minute time-second [time-utc]
  time-hour    = 2DIGIT        ;00-23
  time-minute  = 2DIGIT        ;00-59
  time-second  = 2DIGIT        ;00-60
  ;The "60" value is used to account for positive "leap" seconds.
  time-utc     = "Z"