docs: DNSSEC migration

[jsoref]

Short description

Small tweaks to DNSSEC migration

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[Habbie]

I have a vague recollection we got rid of that modulation code, but somebody would have to check.

[miodvallat]

Well I see explicit replacement of rsa-sha1-nsec3-sha1 (algo 7) with rsa-sha1 (algo 5) in pdnsutil for both import-zone-key and import-zone-key-pem commands, so I am tempted to believe this still applies.

There's a similer replacement in the API, prefixed with

     // TODO remove in 4.2.0

so I suppose there have been plans to stop doing that, but they were never completed.

[coveralls]

Pull Request Test Coverage Report for Build 13444956564

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 45 unchanged lines in 8 files lost coverage.
• Overall coverage increased (+3.8%) to 64.499%

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Files with Coverage Reduction	New Missed Lines	%
modules/gpgsqlbackend/gpgsqlbackend.cc	1	88.62%
ext/json11/json11.cpp	2	62.72%
pdns/distributor.hh	2	51.86%
pdns/misc.cc	2	62.73%
pdns/recursordist/rec-tcpout.cc	6	50.79%
pdns/dnsdistdist/dnsdist-tcp.cc	8	75.82%
pdns/recursordist/test-syncres_cc1.cc	8	89.22%
modules/lmdbbackend/lmdbbackend.cc	16	72.88%

Totals
Change from base Build 13433765276:	3.8%
Covered Lines:	127626
Relevant Lines:	166905

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💛 - Coveralls