Fix PTM stable latest related to the default.qubit.legacy (#966)

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------------------------------------------------------------------------------------------------------------

**Context:**
The CIs on the PTM fail due to incompatibilities between deprecated
devices.

**Description of the Change:**

The PTM has an unexpected behaviour for Stable Lightnin - Latest
PennyLane because on CIs still using the device default.qubit.legacy.
The solution is patching tests following deprecation which will be
removed after v0.39.

**Benefits:**
No more errors in the PTM stable-latest regarding the
`default.qubit.legacy`

**Possible Drawbacks:**

**Related GitHub Issues:**
[sc-76902]

---------

Co-authored-by: ringo-but-quantum <[email protected]>

.github/CHANGELOG.md

@@ -131,6 +131,9 @@
 
 ### Bug fixes
 
+*  Fix PTM stable latest related to `default.qubit.legacy`. 
+  [(#966)](https://github.com/PennyLaneAI/pennylane-lightning/pull/966)
+
 * Fix build failure for Lightning-Kokkos editable installation on MacOS due to `liblightning_kokkos_catalyst.so` copy.
   [(#947)](https://github.com/PennyLaneAI/pennylane-lightning/pull/947)
 

.github/workflows/tests_lgpumpi_python.yml

@@ -142,6 +142,13 @@ jobs:
           git checkout $(git branch -a --list "origin/v0.*rc*" | sort | tail -1)
           python -m pip uninstall -y pennylane && python -m pip install . -vv --no-deps
 
+      - name: Patching tests following deprecation FIXME(remove after v0.39)
+        if: inputs.lightning-version == 'stable' && inputs.pennylane-version == 'latest'
+        run: |
+          pushd mpitests
+          grep -rl "default.qubit.legacy" . | xargs sed -i "s|default.qubit.legacy|default.qubit|g";
+          popd
+  
       - name: Build and install package
         env:
           CUQUANTUM_SDK: $(python -c "import site; print( f'{site.getsitepackages()[0]}/cuquantum')")

.github/workflows/tests_lkcpu_python.yml

@@ -191,6 +191,12 @@ jobs:
           git log -1 --format='%H'
           git status
 
+      - name: Patching tests following deprecation FIXME(remove after v0.39)
+        if: inputs.lightning-version == 'stable' && inputs.pennylane-version == 'latest'
+        run: |
+          pushd tests
+          grep -rl "default.qubit.legacy" . | xargs sed -i "s|default.qubit.legacy|default.qubit|g";
+          popd
 
       - uses: actions/download-artifact@v4
         with:

.github/workflows/tests_lkcuda_python.yml

@@ -260,6 +260,14 @@ jobs:
           PL_BACKEND=${{ matrix.pl_backend }} CMAKE_ARGS="-DCMAKE_PREFIX_PATH=${{ github.workspace }}/Kokkos" \
           python -m pip install . -vv
 
+      - name: Patching tests following deprecation FIXME(remove after v0.39)
+        if: inputs.lightning-version == 'stable' && inputs.pennylane-version == 'latest'
+        run: |
+          cd main/
+          pushd tests
+          grep -rl "default.qubit.legacy" . | xargs sed -i "s|default.qubit.legacy|default.qubit|g";
+          popd
+  
       - name: Run PennyLane-Lightning unit tests
         if: ${{ matrix.pl_backend != 'all'}}
         env:

pennylane_lightning/core/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.39.0-dev50"
+__version__ = "0.39.0-dev51"