Removing Build Scripts for Notifications Plugin

[adityaj1107]

Description

This PR removes the build scripts for the Notifications and the Notifications Dashboard since we have a PR to add them directly to the notifications project (opensearch-project/notifications#398). We are removing them since these take precedence.

Issues Resolved

#1933

Check List

• Commits are signed per the DCO using --signoff

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.60%. Comparing base (5e82386) to head (5bf1549).
⚠️ Report is 2598 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #1938   +/-   ##
=========================================
  Coverage     94.60%   94.60%           
  Complexity       20       20           
=========================================
  Files           178      178           
  Lines          3633     3633           
  Branches         27       27           
=========================================
  Hits           3437     3437           
  Misses          192      192           
  Partials          4        4           

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Waiting for other PR to get merged first

[peterzhuamazon]

We will close this PR because due to BE notifications have 2 level2 subfolders within level1 subfolder, the scripts will current sit in build repo.