let's get rid of `sigma`

See #3147, release log:

• be4c314 by @rultor: Merge branch '__rultor'
• a71be6d by @maxonfjvipon: fix(#3147): param
• 33465e6 by @maxonfjvipon: fix(#3147): finish?
• 1a20501 by @maxonfjvipon: Merge branch 'master' into fix...
• d1e79ba by @rultor: Merge branch '__rultor'
• 2f0d2e7 by @rultor: Merge branch '__rultor'
• 5e662df by @maxonfjvipon: fix(#3147): jtcop
• d1c00dd by @maxonfjvipon: fix(#3147): lowercased auto ge...
• 8e3997b by @yegor256: Merge branch 'master' of githu...
• 5b1f54a by @c71n93: #2978 add assertion messages
• 3cfb4c1 by @c71n93: #2978 enabled tests for dataiz...
• 281d9ed by @c71n93: #2979 enable dataization outpu...
• 676f7ae by @yegor256: doc
• d59f0c9 by @yegor256: doc
• 0b981f6 by @yegor256: doc
• 338c8bc by @yegor256: doc
• 972502e by @yegor256: doc
• 0a3000b by @yegor256: jtcop simplified config
• 3fa635b by @yegor256: we are online
• d35a829 by @maxonfjvipon: fix(#3169): decapitalize phi
• and 151 more...

Released by Rultor 2.0-SNAPSHOT, see build log