FINERACT-2780: Remove obsolete MIX tables from static database SQL dumps

[DhroovSankla]

Description

This Pull Request resolves FINERACT-2780 by cleaning up leftover references to the deleted MIX tables (mix_taxonomy, mix_taxonomy_mapping, and mix_xbrl_namespace) from the static SQL initialization dumps:

1. fineract-provider/src/main/resources/sql/migrations/sample_data/barebones_db.sql
2. fineract-provider/src/main/resources/sql/migrations/sample_data/load_sample_data.sql

All references to create, drop, and insert into these tables have been removed. Constraints and keys for the unrelated m_product_mix table have been preserved as they belong to the active Product Mix feature.

Impact

• Cleans up database schema dumps to be in sync with the codebase after the MIX XBRL reporting module was removed in FINERACT-2745.
• Prevents orphan/obsolete tables from being created when spinning up a fresh database using the static SQL dumps.

Verifications

• Spotless formatting applied: ./gradlew spotlessApply
• Verification tasks completed successfully: ./gradlew :fineract-provider:compileJava :fineract-provider:checkstyleMain

[DhroovSankla]

@adamsaghy
Looking forward for your review!