cli/command/system: fix "docker events" not supporting --format=json

[thaJeztah]

• relates to Add --format=json to inspect and list commands #2936

Before this patch:

docker events --format=json
json
json
json
^C

With this patch:

docker events --format=json
{"status":"create","id":"4ac3bba8abd68961e627540fed81ad16d55b88e45629d7cdb792126d09b6488d","from":"hello-world","Type":"container","Action":"create","Actor":{"ID":"4ac3bba8abd68961e627540fed81ad16d55b88e45629d7cdb792126d09b6488d","Attributes":{"image":"hello-world","name":"dreamy_goldstine"}},"scope":"local","time":1693168508,"timeNano":1693168508190136885}
{"status":"attach","id":"4ac3bba8abd68961e627540fed81ad16d55b88e45629d7cdb792126d09b6488d","from":"hello-world","Type":"container","Action":"attach","Actor":{"ID":"4ac3bba8abd68961e627540fed81ad16d55b88e45629d7cdb792126d09b6488d","Attributes":{"image":"hello-world","name":"dreamy_goldstine"}},"scope":"local","time":1693168508,"timeNano":1693168508192851593}
{"Type":"network","Action":"connect","Actor":{"ID":"c54920dd5074a73e28bea62007e0334d81cc040a90372be311cf16806403d350","Attributes":{"container":"4ac3bba8abd68961e627540fed81ad16d55b88e45629d7cdb792126d09b6488d","name":"bridge","type":"bridge"}},"scope":"local","time":1693168508,"timeNano":1693168508212398802}
{"status":"start","id":"4ac3bba8abd68961e627540fed81ad16d55b88e45629d7cdb792126d09b6488d","from":"hello-world","Type":"container","Action":"start","Actor":{"ID":"4ac3bba8abd68961e627540fed81ad16d55b88e45629d7cdb792126d09b6488d","Attributes":{"image":"hello-world","name":"dreamy_goldstine"}},"scope":"local","time":1693168508,"timeNano":1693168508312969843}
^C

- What I did

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- Description for the changelog

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[codecov-commenter]

Codecov Report

Merging #4530 (a0121f6) into master (a1367a0) will increase coverage by 0.27%.
The diff coverage is 81.25%.

Additional details and impacted files

@@ Coverage Diff @@## master #4530 +/- ##
==========================================
+ Coverage 59.38% 59.66% +0.27% 
==========================================
Files 288 286 -2 Lines 24785 24782 -3 ==========================================
+ Hits 14718 14785 +67 + Misses 9186 9111 -75 - Partials 881 886 +5