Remove attempt to use non-existing .issues property

I think it never worked, and the API docs do not mention it (only the single .issue property),
and either way this usage here does not seem helpful, issue/description still contains the same unfriendly text as in the exception message already

modules/ppcp-api-client/src/Exception/PayPalApiException.php

@@ -111,15 +111,6 @@ class PayPalApiException extends RuntimeException {
 		return false;
 	}
 
-	/**
-	 * Returns response issues.
-	 *
-	 * @return array
-	 */
-	public function issues(): array {
-		return $this->response->issues ?? array();
-	}
-
 	/**
 	 * The HTTP status code.
 	 *

modules/ppcp-wc-gateway/src/Gateway/ProcessPaymentTrait.php

@@ -229,22 +229,11 @@ trait ProcessPaymentTrait {
 				);
 			}
 
-			$error_message = $error->getMessage();
-			if ( $error->issues() ) {
-				$error_message = implode(
-					array_map(
-						function( $issue ) {
-							return $issue->issue . ' ' . $issue->description . '<br/>';
-						},
-						$error->issues()
-					)
-				);
-			}
-
 			return $this->handle_payment_failure(
 				$wc_order,
 				new Exception(
-					$error_message,
+					__( 'Failed to process the payment. Please try again or contact the shop admin.', 'woocommerce-paypal-payments' )
+					. ' ' . $error->getMessage(),
 					$error->getCode(),
 					$error
 				)