Reverted unnecessary change

Author: Alex-Nita

service/src/main/java/uk/nhs/adaptors/gp2gp/ehr/mapper/diagnosticreport/DiagnosticReportMapper.java

@@ -133,7 +133,7 @@ private List<Specimen> fetchSpecimens(DiagnosticReport diagnosticReport, List<Ob
             .map(specimenReference -> inputBundleHolder.getResource(specimenReference.getReferenceElement()))
             .flatMap(Optional::stream)
             .map(Specimen.class::cast)
-            .toList();
+            .collect(Collectors.toList());
 
         specimens.addAll(preExistingSpecimens);