Ignore error about by ref constraint

This part of the code is too convoluted for Psalm (and maybe for humans
too).

psalm.xml

@@ -23,6 +23,15 @@
         <file name="vendor/jetbrains/phpstorm-stubs/sqlsrv/sqlsrv.php" />
     </stubs>
     <issueHandlers>
+        <ConflictingReferenceConstraint>
+            <errorLevel type="suppress">
+                <!--
+                    This one is just too convoluted for Psalm to figure out, by
+                    its author's own admission
+                -->
+                <file name="lib/Doctrine/DBAL/Driver/OCI8/OCI8Statement.php"/>
+            </errorLevel>
+        </ConflictingReferenceConstraint>
         <TooFewArguments>
             <errorLevel type="suppress">
                 <!--