C++: Remove getFullyConverted call in sink def

With this change, the `IRDataflowTestCommon.qll` and
`DataflowTestCommon.qll` files use the same definitions of sources and
sinks. Since the IR data flow library is meant to be compatible with the
AST data flow library, this is what we ought to be testing.

Two alerts change but not necessarily for the right reasons.

Author: jbj

cpp/ql/test/library-tests/dataflow/dataflow-tests/IRDataflowTestCommon.qll

@@ -19,7 +19,7 @@ class TestAllocationConfig extends DataFlow::Configuration {
   override predicate isSink(DataFlow::Node sink) {
     exists(FunctionCall call |
       call.getTarget().getName() = "sink" and
-      sink.asExpr() = call.getAnArgument().getFullyConverted()
+      sink.asExpr() = call.getAnArgument()
     )
   }
 

cpp/ql/test/library-tests/dataflow/dataflow-tests/test_diff.expected

@@ -1,5 +1,5 @@
 | test.cpp:66:30:66:36 | test.cpp:71:8:71:9 | AST only |
-| test.cpp:89:28:89:34 | test.cpp:90:8:90:14 | AST only |
+| test.cpp:89:28:89:34 | test.cpp:92:8:92:14 | IR only |
 | test.cpp:100:13:100:18 | test.cpp:103:10:103:12 | AST only |
 | test.cpp:120:9:120:20 | test.cpp:126:8:126:19 | AST only |
 | test.cpp:122:18:122:30 | test.cpp:132:22:132:23 | IR only |

cpp/ql/test/library-tests/dataflow/dataflow-tests/test_ir.expected

@@ -9,6 +9,8 @@
 | test.cpp:76:8:76:9 | Load: u1 | test.cpp:75:7:75:8 | Uninitialized: definition of u1 |
 | test.cpp:84:8:84:18 | Load: ... ? ... : ... | test.cpp:83:7:83:8 | Uninitialized: definition of u2 |
 | test.cpp:86:8:86:9 | Load: i1 | test.cpp:83:7:83:8 | Uninitialized: definition of u2 |
+| test.cpp:90:8:90:14 | Load: source1 | test.cpp:89:28:89:34 | InitializeParameter: source1 |
+| test.cpp:92:8:92:14 | Load: source1 | test.cpp:89:28:89:34 | InitializeParameter: source1 |
 | test.cpp:132:22:132:23 | Load: m1 | test.cpp:122:18:122:30 | InitializeParameter: sourceStruct1 |
 | test.cpp:140:22:140:23 | Load: m1 | test.cpp:122:18:122:30 | InitializeParameter: sourceStruct1 |
 | test.cpp:188:8:188:8 | Load: y | test.cpp:186:27:186:32 | Call: call to source |