IndexError while parsing a cc payment using paypal

[gauravsaini23]

https://github.com/Shopify/active_merchant/blob/master/lib/active_merchant/billing/gateways/paypal/paypal_common_api.rb#L435

This error is raised because xml tag value is 'SOAP_ENV:Envelope' and not 'Envelope'.
Due to this, cc payment always fails.

[davidsantoso]

@gauravsaini23 closing due to staleness and all remote tests passing:

➜ ruby -Itest test/remote/gateways/remote_paypal_test.rb
Loaded suite test/remote/gateways/remote_paypal_test
Started
..........................

Finished in 178.558084 seconds.
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26 tests, 74 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
100% passed
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
0.15 tests/s, 0.41 assertions/s