ci: vendor validation scripts and remove remote action pins (#84)

Automated PR to fix CI after deleted actions.

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## Summary by Gitar

- **Server features:**
- Added `/api/explain` endpoint for analyzing query plans on semantic
and raw SQL queries
- Integrated index creation via `Skein.create_index!` for semantic index
columns
- **Beam updates:**
- Added test coverage threshold and test/dev dependencies in `mix.exs`

<sub>This will update automatically on new commits.</sub>

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Signed-off-by: Jonathan D.A. Jewell <6759885+hyperpolymath@users.noreply.github.com>

Author: hyperpolymath

beam/mix.exs

@@ -8,7 +8,11 @@ defmodule QuandleDBNif.MixProject do
       elixir: "~> 1.18",
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),
-      deps: deps()
+      deps: deps(),
+      test_coverage: [
+        summary: [threshold: 90],
+        ignore_modules: [QuandleDBNif.Native]
+      ]
     ]
   end