Upgraded Newtonsoft Json dependency to fix severe vulnerability issue

[MiroKentico]

Motivation

Updated Newtonsoft.Json dependency to recommended version to fix severe vulnerability issue. Fixes #338.

[codecov]

Codecov Report

Merging #340 (ce790d5) into master (8f43f7f) will decrease coverage by 4.55%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #340      +/-   ##
==========================================
- Coverage   93.66%   89.10%   -4.56%     
==========================================
  Files         120      120              
  Lines        2589     2589              
  Branches      321      318       -3     
==========================================
- Hits         2425     2307     -118     
- Misses        157      163       +6     
- Partials        7      119     +112     

Impacted Files	Coverage Δ
Kentico.Kontent.Delivery.Caching/StringHelpers.cs	83.33% <0.00%> (-16.67%)	⬇️
Kentico.Kontent.Delivery.Caching/CacheHelpers.cs	81.53% <0.00%> (-14.62%)	⬇️
Kentico.Kontent.Delivery/DeliveryException.cs	57.14% <0.00%> (-14.29%)	⬇️
...ontent.Delivery.Caching/DistributedCacheManager.cs	61.36% <0.00%> (-13.64%)	⬇️
...livery/Extensions/HttpResponseHeadersExtensions.cs	88.88% <0.00%> (-11.12%)	⬇️
...ico.Kontent.Delivery.Rx/DeliveryObservableProxy.cs	78.94% <0.00%> (-10.53%)	⬇️
...y/ContentItems/ContentLinks/ContentLinkResolver.cs	73.46% <0.00%> (-10.21%)	⬇️
...co.Kontent.Delivery.Caching/DeliveryClientCache.cs	85.50% <0.00%> (-10.15%)	⬇️
...nt.Urls/Delivery/QueryParameters/OrderParameter.cs	90.00% <0.00%> (-10.00%)	⬇️
...ico.Kontent.Delivery.Caching/MemoryCacheManager.cs	71.42% <0.00%> (-9.90%)	⬇️
... and 17 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8f43f7f...ce790d5. Read the comment docs.

[Sevitas]

Approved, with a suggestion.
Have you thought about updating other packages as well? There is quite a lot of packages needing an upgrade, some of them require consolidation.

[MiroKentico]

Approved, with a suggestion. Have you thought about updating other packages as well? There is quite a lot of packages needing an upgrade, some of them require consolidation.

To be honest, I didn't thought of this, but I created separated #342 for this. Feel free to suggest packages that you have in mind to this issue.