fix(deps): update dependency mqtt to v4

[renovate-bot]

This PR contains the following updates:

Package	Type	Update	Change
mqtt	dependencies	major	^3.0.0 -> ^4.0.0

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Release Notes

mqttjs/MQTT.js

v4.0.0

Compare Source

• refactor: callbacks on end() (#​1080)
• chore: change workflow to v10-14 and doc fixes (#​1079)
• feat(client): error handling and test resilience (#​1076)
• chore: add master branch action (#​1062)
• chore: istanbul to nyc and uglify-js to uglify-es (#​1061)
• chore: github actions (#​1059)
• feat: connection error handler (#​1053)
• fix: remove only (#​1058)
• feat: support SNI on TLS (#​1055)
• chore: tidy up debug logs (#​1052)
• fix various options definition for ts usage (#​1043)
• refactor: zuul to airtap for browser testing (#​1045)

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