Use : for time and showtime msg formatting

[IanButterworth]

As suggested in #42431 (comment)

Changes -> to : and removes the left-padding on the time report when a description is provided

julia> @showtime sleep(1)
sleep(1): 1.002159 seconds (286 allocations: 15.273 KiB)

julia> @time "description" sleep(1)
description: 1.002132 seconds (5 allocations: 144 bytes)

julia> @time sleep(1)
  1.001287 seconds (5 allocations: 144 bytes)

[IanButterworth]

FreeBSD error is HTTPBingo flakiness