bwauth: update measured bandwidth file comments

[teor2345]

We forgot to update function header comments and code comments when we
made changes in 0.3.5.1-alpha and later.

Closes 30112.

[coveralls]

Pull Request Test Coverage Report for Build 4660

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 240 unchanged lines in 15 files lost coverage.
• Overall coverage decreased (-0.3%) to 62.268%

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Files with Coverage Reduction	New Missed Lines	%
src/feature/nodelist/nodelist.c	2	71.88%
src/lib/buf/buffers.c	2	90.93%
src/feature/rend/rendcache.c	2	93.02%
src/lib/fs/files.c	2	67.21%
src/feature/relay/router.c	2	51.07%
src/app/config/statefile.c	3	52.44%
src/feature/relay/routermode.c	3	50.0%
src/lib/net/buffers_net.c	6	75.9%
src/app/config/confparse.c	8	78.56%
src/feature/stats/rephist.c	9	43.69%

Totals
Change from base Build 4655:	-0.3%
Covered Lines:	46192
Relevant Lines:	74182

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💛 - Coveralls