[REF] remove first attempt to set currency in repeattransaction flow

The currency is retrieved from the template transaction, these lines are no longer needed, as demonstrated
in the test

CRM/Contribute/BAO/Contribution.php

@@ -4462,11 +4462,6 @@ public static function completeOrder($input, &$ids, $objects, $isPostPaymentCrea
     ], array_intersect_key($input, array_fill_keys($inputContributionWhiteList, 1)
     ));
 
-    // CRM-20678 Ensure that the currency is correct in subseqent transcations.
-    if (empty($contributionParams['currency']) && isset($objects['first_contribution']->currency)) {
-      $contributionParams['currency'] = $objects['first_contribution']->currency;
-    }
-
     $contributionParams['payment_processor'] = $input['payment_processor'] = $paymentProcessorId;
 
     // If paymentProcessor is not set then the payment_instrument_id would not be correct.

tests/phpunit/CRM/Contribute/BAO/ContributionRecurTest.php

@@ -227,7 +227,7 @@ public function testGetTemplateContributionNewTemplate() {
       'financial_type_id' => 1,
       'source' => 'Template Contribution',
       'payment_instrument_id' => 1,
-      'currency' => 'USD',
+      'currency' => 'AUD',
       'contact_id' => $this->individualCreate(),
       'contribution_status_id' => 1,
       'receive_date' => 'yesterday',