chore: remove accidentally committed github runner migration

Remove the github_runner_sources migration that was accidentally
included in the health check status fix branch. This migration
is unrelated to the health check functionality and should be
developed separately.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

database/migrations/2025_11_19_115504_create_github_runner_sources_table.php

@@ -1,27 +0,0 @@
-<?php
-
-use Illuminate\Database\Migrations\Migration;
-use Illuminate\Database\Schema\Blueprint;
-use Illuminate\Support\Facades\Schema;
-
-return new class extends Migration
-{
-    /**
-     * Run the migrations.
-     */
-    public function up(): void
-    {
-        Schema::create('github_runner_sources', function (Blueprint $table) {
-            $table->id();
-            $table->timestamps();
-        });
-    }
-
-    /**
-     * Reverse the migrations.
-     */
-    public function down(): void
-    {
-        Schema::dropIfExists('github_runner_sources');
-    }
-};