Update beats framework to 6e91ce4988a7 fixes duplicate dynamic template names

[simitt]

Motivation/summary

Pull in beats update to fix duplicate name issue for dynamic templates, #2693.

This upgrade also changes the fixed version of k8s.io/client-go to v0.18.3 and upgrades grpc and protobuf libraries to stay compatible with libbeat.

Checklist

- [ ] I have signed the Contributor License Agreement.

• I have updated CHANGELOG.asciidoc

I have considered changes for:
- [ ] documentation
- [ ] logging (add log lines, choose appropriate log selector, etc.)
- [ ] metrics and monitoring (create issue for Kibana team to add metrics to visualizations, e.g. Kibana#44001)

• automated tests (add tests for the code changes, all unit tests pass locally)
  - [ ] telemetry
  - [ ] Elasticsearch Service (https://cloud.elastic.co)
  - [ ] Elastic Cloud Enterprise (https://www.elastic.co/products/ece)
  - [ ] Elastic Cloud on Kubernetes (https://www.elastic.co/elastic-cloud-kubernetes)

How to test these changes

see description in beats PR elastic/beats#18849

Related issues

closes #2693

[apmmachine]

💚 Build Succeeded

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Build stats

• Build Cause: [Pull request #3832 updated]

• Start Time: 2020-06-02T10:48:36.048+0000

• Duration: 45 min 59 sec

Test stats 🧪

Test	Results
Failed	0
Passed	3201
Skipped	146
Total	3347

[codecov-commenter]

Codecov Report

Merging #3832 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3832      +/-   ##
==========================================
+ Coverage   79.59%   79.64%   +0.04%     
==========================================
  Files         135      135              
  Lines        6142     6142              
==========================================
+ Hits         4889     4892       +3     
+ Misses       1253     1250       -3     

Impacted Files	Coverage Δ
beater/jaeger/common.go	78.78% <0.00%> (-6.07%)	⬇️
kibana/connecting_client.go	72.58% <0.00%> (+8.06%)	⬆️