Update V2 Zowe Explorer README GIFs and remove keytar notice

[adam-wolfe]

Proposed changes

Replace old gifs in the Zowe Explorer README.md with new ones from Zowe Docs and remove the keytar notice, since it has been over a year since keytar was replaced.

Remove unused gifs.

Release Notes

Milestone: 2.17.0

Changelog: n/a

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds or improves functionality)
• Breaking change (a change that would cause existing functionality to not work as expected)
• Documentation (Markdown, README updates)
• Other (please specify above in "Proposed changes" section)

Checklist

General

• I have read the CONTRIBUTOR GUIDANCE wiki
• All PR dependencies have been merged and published (if applicable)
• A GIF or screenshot is included in the PR for visual changes
• The pre-publish command has been executed:
  • v2 and below: yarn workspace vscode-extension-for-zowe vscode:prepublish
  • v3: pnpm --filter vscode-extension-for-zowe vscode:prepublish

Code coverage

• There is coverage for the code that I have added
• I have added new test cases and they are passing
• I have manually tested the changes

Deployment

• I have added developer documentation (if applicable)
• Documentation should be added to Zowe Docs
  • If you're an outside contributor, please post in the #zowe-doc Slack channel to coordinate documentation.
  • Otherwise, please check with the rest of the squad about any needed documentation before merging.
• These changes may need ported to the appropriate branches (list here):

Further comments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.54%. Comparing base (141289c) to head (d495149).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2997   +/-   ##
=======================================
  Coverage   93.54%   93.54%           
=======================================
  Files         104      104           
  Lines       10889    10889           
  Branches     2386     2367   -19     
=======================================
  Hits        10186    10186           
  Misses        702      702           
  Partials        1        1           

☔ View full report in Codecov by Sentry.
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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[t1m0thyj]

Thanks @adam-wolfe, the new GIFs look great!

[traeok]

LGTM, thanks for updating the readme and GIFs @adam-wolfe!