[Chapel Merge] Replace explicit ends of the region in the fileIO

Branch: refs/heads/main
Revision: 3983a1c
Author: lydia-duncan
Link: Replace explicit ends of the region in the fileIO primer with the count operator by lydia-duncan · Pull Request #20670 · chapel-lang/chapel · GitHub
Log Message:

Merge pull request #20670 from lydia-duncan/cleanupPrimer

Replace explicit ends of the region in the fileIO primer with the count operator
[okay'd by @bradcray]

Brad pointed out that since these were computed as a set number past the start point, the count operator would also accomplish the same thing and could be naturally used in the expression. This impacted two places in the primer.

Note: we noticed that the end of the region probably should have a different meaning than it does today.
This PR does not address that but it is tracked in #20672 and I do intend to get to it soon.

Verified a fresh checkout

Modified Files:
M test/release/examples/primers/fileIO.chpl

Compare: https://github.com/chapel-lang/chapel/compare/404e5caa96d1...3983a1cc1f9d