[canada] - bank_code_length 4 -> 3

[piiraa]

The changes permit the input of CA details using a 3-digit bank code.

This should not affect the underlying systems, as the previous value is still accepted (4 digits). Additionally, the pseudo_iban_bank_code_length ensures that the returned value remains 4 digits long.

iban1 = Ibandit::IBAN.new(country_code: 'CA', bank_code: '0036', branch_code: '00063', account_number: '0123456')
=> #<Ibandit::IBAN:0x0000000104c99f78
 @account_number="0123456",
 @bank_code="0036",
 @branch_code="00063",
 @country_code="CA",
 @errors={},
 @iban=nil,
 @source=:local_details,
 @swift_account_number="0123456",
 @swift_bank_code="0036",
 @swift_branch_code="00063">
 
iban2 = Ibandit::IBAN.new(country_code: 'CA', bank_code: '036', branch_code: '00063', account_number: '0123456')
=> #<Ibandit::IBAN:0x0000000104c978b8
 @account_number="0123456",
 @bank_code="0036",
 @branch_code="00063",
 @country_code="CA",
 @errors={},
 @iban=nil,
 @source=:local_details,
 @swift_account_number="0123456",
 @swift_bank_code="0036",
 @swift_branch_code="00063">
 
iban1.pseudo_iban == iban2.pseudo_iban
=> true

iban1.bank_code
=> "0036"

iban2.bank_code
=> "0036"