Upgrade to Vert.x 3.9.1

[malaskowski]

Description

Upgrade Vert.x to 3.9.1

Motivation and Context

https://github.com/Knotx/knotx-dependencies/issues/48

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] I have read the CONTRIBUTING document.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.

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I hereby agree to the terms of the Knot.x Contributor License Agreement.

[codecov[bot]]

Codecov Report

Merging #47 into master will not change coverage. The diff coverage is 0.00%.

@@            Coverage Diff            @@
##             master      #47   +/-   ##
=========================================
  Coverage     70.08%   70.08%           
  Complexity      109      109           
=========================================
  Files            20       20           
  Lines           488      488           
  Branches          6        6           
=========================================
  Hits            342      342           
  Misses          140      140           
  Partials          6        6           

Impacted Files	Coverage Δ	Complexity Δ
...main/java/io/knotx/te/core/TemplateEngineKnot.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)

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