When you want to change the definition of a database enum from a Laravel migration, you can do it like this:

Schema::table('jobs', function (Blueprint $table) {
    $table->enum('type', ['contract', 'permanent', 'partial'])->change();
});

Be aware though that support for this depends on the database engine. For MySQL, this is supported, for PostgreSQL and SQL Server, it's not as explained here:

Supported databases, modifiers and types:

Database Native Support Supported column modifiers Supported column types
MariaDB ✅ (docs) Same as MySQL All types
MySQL ✅ (docs) after, first, autoIncrement, from, storedAs, storedAsJson, virtualAs, virtualAsJson, invisible, unsigned, nullable, default, charset, collation, comment, useCurrent, useCurrentOnUpdate, srid, renameTo All types
PostgreSQL ✅ (docs) autoIncrement, from, storedAs, generatedAs, always, nullable, default, collation, comment, useCurrent, isGeometry, projection All types except enum
SQLite ❌ (docs) N/A N/A
SQL Server ✅ (docs) autoIncrement, nullable, default, collation, persisted, useCurrent All types except enum