Upgrade express version

[helzahalim]

Bump express version to above 4.20.0.
Version 4.19.2 has introduced multiple Snyk Vulnerability

1. Introduced through: @slack/bolt@3.21.4 › express@4.19.2 › path-to-regexp@0.1.7
   CVSS v4.0 6.9

2. Introduced through: @slack/bolt@3.21.4 › express@4.19.2 › body-parser@1.20.2
   CVSS v4.0 8.2

3. Introduced through: @slack/bolt@3.21.4 › express@4.19.2
   CVSS v4.0 5.1

4. Introduced through : @slack/bolt@3.21.4 › express@4.19.2 › send@0.18.0
   CVSS v4.0 2.1

5. Introduced through: @slack/bolt@3.21.4 › express@4.19.2 › serve-static@1.15.0
   CVSS v4.0 2.1

Summary

Describe the goal of this PR. Mention any related Issue numbers.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.78%. Comparing base (e82f6e8) to head (07864de).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2270   +/-   ##
=======================================
  Coverage   87.78%   87.78%           
=======================================
  Files          19       19           
  Lines        1646     1646           
  Branches      464      464           
=======================================
  Hits         1445     1445           
  Misses        194      194           
  Partials        7        7           

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[filmaj]

Thank you!