[tests] Fix test (#6362)

**Context:** Fixes compiler test after changes in Catalyst.

**Description of the Change:** Catalyst will now have a public function
inside a quantum module to denote the entry point into the qnode.

**Benefits:** Tests pass when running with latest Catalyst.

**Possible Drawbacks:** None

**Related GitHub Issues:**

doc/releases/changelog-dev.md

@@ -278,6 +278,9 @@
   [(#6278)](https://github.com/PennyLaneAI/pennylane/pull/6278)
   [(#6310)](https://github.com/PennyLaneAI/pennylane/pull/6310)
 
+* Fixes a test after updating to the nightly version of Catalyst.
+  [(#6362)](https://github.com/PennyLaneAI/pennylane/pull/6362)
+
 <h3>Contributors ✍️</h3>
 
 This release contains contributions from (in alphabetical order):
@@ -295,6 +298,7 @@ Austin Huang,
 Korbinian Kottmann,
 Christina Lee,
 William Maxwell,
+Erick Ochoa Lopez,
 Lee J. O'Riordan,
 Mudit Pandey,
 David Wierichs,

tests/test_compiler.py

@@ -246,7 +246,7 @@ def circuit(x: float):
             return qml.expval(qml.PauliZ(0))
 
         mlir_str = str(circuit.mlir)
-        result_header = "func.func private @circuit(%arg0: tensor<f64>) -> tensor<f64>"
+        result_header = "func.func public @circuit(%arg0: tensor<f64>) -> tensor<f64>"
         assert result_header in mlir_str
 
     def test_qjit_adjoint(self):