Upgrade local Elasticsearch from 7.4 to 7.7

[alexm118]

Upgrades our local Elasticsearch version from 7.4 to 7.7 to reduce the number of twistlock vulnerabilities being reported.

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Changes

• Alpine Elasticsearch base image from 7.4 -> 7.7
• Alpine Kibana image from 7.4 -> 7.7

How to test this PR

1. Run the stack locally

Checklist

• PR has an informative and human-readable title
  • PR titles are used to generate the change log in releases; good ones make that easier to scan.
  • Consider prefixing, e.g., "Mega Menu: fix layout bug", or "Docs: Update Docker installation instructions".
• Changes are limited to a single goal (no scope creep)
• Code follows the standards laid out in the CFPB development guidelines
• Future todos are captured in comments and/or tickets
• Project documentation has been updated, potentially one or more of:
  • This repo’s docs (edit the files in the /docs folder) – for basic, close-to-the-code docs on working with this repo
  • CFGOV/platform wiki on GHE – for internal CFPB developer guidance
  • CFPB/hubcap wiki on GHE – for internal CFPB design and content guidance