doc/server.md: docker, how to update?

5 jobs for dev in 6 minutes and 7 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test Tools
passed #184383
test_tools

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  Test Quality
passed #184384
web
code_quality

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  Test Unit
passed #184385
web
test_browser_unit

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passed #184386
web
test_server_unit

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  Test Functional
passed #184387
docker x86_64
test_server_functional

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