custom Docker image is not used after building

See #1861, release log:

• 400a547 by @rultor: Merge branch '__rultor'
• 8062e4c by @yegor256: push
• 49e2634 by @yegor256: dokku
• ed2ebf5 by @renovate[bot]: chore(deps): update dependency...
• f700e3c by @yegor256: token
• 0feeeee by @yegor256: #1861 fixed
• f218819 by @rultor: Merge branch '__rultor'
• 20a76e3 by @renovate[bot]: fix(deps): update slf4j monore...
• 834b576 by @renovate[bot]: fix(deps): update aws-java-sdk...
• 2681197 by @renovate[bot]: fix(deps): update dependency c...
• 83d9c83 by @rultor: Merge branch '__rultor'
• 78bf9d3 by @renovate[bot]: fix(deps): update dependency o...
• 152a718 by @renovate[bot]: fix(deps): update dependency o...
• 9519c34 by @yegor256: loc off
• 79ad55e by @rultor: Merge branch '__rultor'
• b623a6b by @renovate[bot]: fix(deps): update dependency c...
• 5a03cc9 by @renovate[bot]: fix(deps): update dependency c...
• 0d0effa by @rultor: Merge branch '__rultor'
• ed650b6 by @rultor: Merge branch '__rultor'
• 4b51c15 by @rultor: Merge branch '__rultor'
• and 148 more...

Released by Rultor 1.75.2, see build log