Add missing log function

[HuskyNator]

Error was missing from the documentation here.

[dlang-bot]

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If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#8846"

[PetarKirov]

@HuskyNator the syntax for DDoc macros is $(MACRO_NAME ARGS), see: https://dlang.org/spec/ddoc#macros

Suggested change

	#(LI `error`)
	$(LI `error`)

[PetarKirov]

@thewilsonator please check the doc tester before merging:

https://dtest.dlang.io/artifact/website-fd7e1f50f4d2329f24313ea92bfcbd91af962cdb-57c7f9baeef70e48134208b01ac92871/web/phobos-prerelease/std_logger.html

[PetarKirov]

I've opened a PR to fix this: #8848