src/TableBlueprint.php
public function dropForeignKey(string $column): self
    {
        return $this->addOperation(
            new Operation\ForeignKey\Drop($this->table, $column)
        );
    }
public function dropForeignKey(string $column): self
    {
        return $this->addOperation(
            new Operation\ForeignKey\Drop($this->table, $column)
        );
    }
Example:
$table->dropForeignKey('user_id');

@param string $column
@return TableBlueprint