[Wiki] Release verification howto is obsolete

[asfimport]

https://cwiki.apache.org/confluence/display/ARROW/How+to+Verify+Release+Candidates#HowtoVerifyReleaseCandidates-LinuxandmacOS

The example commands are wrong.
E.g.,

TEST_DEFAULT=0 TEST_SOURCE=1 TEST_CPP=1 verify-release-candidate.sh source $VERSION $RC_NUM

should be changed to

TEST_DEFAULT=0 TEST_CPP=1 verify-release-candidate.sh $VERSION $RC_NUM

Reporter: Yibo Cai / @cyb70289

_{Note: This issue was originally created as ARROW-16353. Please see the migration documentation for further details.}

[asfimport]

Yibo Cai / @cyb70289:
Looks I cannot edit the wiki, though the confluence page Restriction says "Everyone can view and edit this page".

[jorisvandenbossche]

We should probably also move this content to the documentation (so everyone can update it through normal PRs), instead of keeping it in the wiki? (like was done for the release guide at https://arrow.apache.org/docs/dev/developers/release.html)
cc @raulcd

[jorisvandenbossche]

Some other inaccuracies / undocumented features that I noticed:

• Re-using the directory requires the ARROW_TMPDIR env variable, and not TMPDIR
• The USE_CONDA=1 option is not mentioned