Island: Remove f-string from MONGO_URL

[ilija-lazoroski]

What does this PR do?

Related to #4170.

PR Checklist

• Have you added an explanation of what your changes do and why you'd like to include them?
• Is the TravisCI build passing?
• Was the CHANGELOG.md updated to reflect the changes?
• Was the documentation framework updated to reflect the changes?
• Have you checked that you haven't introduced any duplicate code?

Testing Checklist

• Added relevant unit tests?
• Do all unit tests pass?
• Do all end-to-end tests pass?
• Any other testing performed?

  Tested by {Running the Monkey locally with relevant config/running Island/...}

• If applicable, add screenshots or log transcripts of the feature working

[VakarisZ]

Suggested change

	"mongodb://{0}:{1}/{2}".format(
	DEFAULT_MONGO_DB_HOST, DEFAULT_MONGO_DB_PORT, DEFAULT_MONGO_DB_NAME
	),
	f"mongodb://{DEFAULT_MONGO_DB_HOST}:{DEFAULT_MONGO_DB_PORT}/{DEFAULT_MONGO_DB_NAME}"

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.07%. Comparing base (3e7073f) to head (2db7e6f).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4174   +/-   ##
========================================
  Coverage    77.07%   77.07%           
========================================
  Files          444      444           
  Lines        14138    14138           
  Branches        18       18           
========================================
  Hits         10897    10897           
  Misses        3241     3241           

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