Update MySqlSchemaAdapter.php

[AntoineMarques]

Generator/PhinxMySqlGenerator::getTableMigrationNewDatabase expects upper case keys.

A notice is thrown, then migration fails with message

PHP Fatal error:  Uncaught TypeError: Argument 1 passed to Odan\Migration\Adapter\Generator\PhinxMySqlGenerator::getAlterDatabaseCharset() must be of the type string, null given, called in /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php on line 194 and defined in /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php:211
Stack trace:
#0 /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php(194): Odan\Migration\Adapter\Generator\PhinxMySqlGenerator->getAlterDatabaseCharset(NULL)
#1 /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php(150): Odan\Migration\Adapter\Generator\PhinxMySqlGenerator->getTableMigrationNewDatabase(Array, Array, Array)
#2 /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php(125): Odan\Migration\Adapter\Generator\PhinxMySqlGenerator->addChangeMethod(Array, Array, Array)
#3  in /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php on line 211

Fatal error: Uncaught TypeError: Argument 1 passed to Odan\Migration\Adapter\Generator\PhinxMySqlGenerator::getAlterDatabaseCharset() must be of the type string, null given, called in /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php on line 194 and defined in /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php on line 211

TypeError: Argument 1 passed to Odan\Migration\Adapter\Generator\PhinxMySqlGenerator::getAlterDatabaseCharset() must be of the type string, null given, called in /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php on line 194 in /app/vendor/odan/phinx-migrations-generator/src/Migration/Adapter/Generator/PhinxMySqlGenerator.php on line 211

[odan]

Thanks!