fix(plugin-dns): remove from default plugin list

[OlivierAlbertini]

Which problem is this PR solving?

• closes Remove Dns plugin from the config  #612

Short description of the changes

• remove dns plugin from the default list
• add doc for Zipkin until with find a solution that let's us ignore http call without specifying in plugin option

[codecov-io]

Codecov Report

Merging #613 into master will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #613      +/-   ##
==========================================
- Coverage   90.44%   90.39%   -0.05%     
==========================================
  Files         181      176       -5     
  Lines        9164     9062     -102     
  Branches      814      792      -22     
==========================================
- Hits         8288     8192      -96     
+ Misses        876      870       -6

Impacted Files	Coverage Δ
packages/opentelemetry-node/src/config.ts	100% <ø> (ø)	⬆️
...ges/opentelemetry-plugin-https/test/utils/utils.ts	33.33% <0%> (-26.67%)	⬇️
.../opentelemetry-plugin-redis/test/assertionUtils.ts	95.83% <0%> (-4.17%)	⬇️
...res/opentelemetry-plugin-pg/test/assertionUtils.ts	96.29% <0%> (-3.71%)	⬇️
...opentelemetry-base/test/resources/resource.test.ts	100% <0%> (ø)	⬆️
packages/opentelemetry-plugin-https/src/utils.ts	100% <0%> (ø)	⬆️
...es/opentelemetry-exporter-collector/test/helper.ts	100% <0%> (ø)	⬆️
...es/opentelemetry-plugin-document-load/src/utils.ts
packages/opentelemetry-metrics/src/types.ts
...y-plugin-document-load/src/enums/AttributeNames.ts
... and 4 more

[mayurkale22]

It would be nice to have note next to DNS plugin here and here.

[mayurkale22]

It would be nice to have note next to DNS plugin here and here.

Let's handle this in separate PR, don't want to block release due to this.