Remove redundant conjunct

Author: owen-mc

go/ql/test/library-tests/semmle/go/dataflow/GlobalVariableSideEffects/Flows.ql

@@ -2,7 +2,6 @@ import go
 import utils.test.InlineFlowTest
 
 string getArgString(DataFlow::Node src, DataFlow::Node sink) {
-  exists(src) and
   result =
     "\"" + sink.toString() + " (from source " +
       src.(DataFlow::CallNode).getArgument(0).getExactValue() + ")\""