Increase Agent's mem limits in k8s

[ChrsMark]

What does this PR do?

This PR increases the limits for elastic-agent running as Pod in Kubernetes.
There have been reports of Agent's Pod being OOMKilled like in elastic/integrations#1354.

cc: @MichaelKatsoulis

[elasticmachine]

Pinging @elastic/integrations (Team:Integrations)

[elasticmachine]

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• Start Time: 2021-08-02T07:08:58.491+0000

• Duration: 96 min 14 sec

• Commit: a8c7609

Test stats 🧪

Test	Results
Failed	0
Passed	7012
Skipped	16
Total	7028

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Test stats 🧪

Test	Results
Failed	0
Passed	7012
Skipped	16
Total	7028

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b increase_mem_limits_agent_k8s upstream/increase_mem_limits_agent_k8s
git merge upstream/master
git push upstream increase_mem_limits_agent_k8s