[R] Make map_batches .lazy = TRUE by default

[asfimport]

arrow/r/R/dataset-scan.R

Lines 249 to 250 in 70904df

	# TODO(ARROW-17178) because there are some restrictions on evaluating
	# reader_out in some ExecPlans, the default .lazy is FALSE for now.

has a note that the default is lazy = FALSE because of ARROW-17178, but that issue has since been resolved.

Reporter: Neal Richardson / @nealrichardson
Assignee: Dewey Dunnington / @paleolimbot

PRs and other links:

• GitHub Pull Request #14521

_{Note: This issue was originally created as ARROW-18012. Please see the migration documentation for further details.}

[asfimport]

Dewey Dunnington / @paleolimbot:
Issue resolved by pull request 14521
#14521