QED openPMD Tests: Specify H5 Backend

We default to ADIOS `.bp` if available. Thus, specify HDF5 assumption

Author: ax3l

Regression/WarpX-tests.ini

@@ -1398,7 +1398,7 @@ tolerance = 1.e-14
 buildDir = .
 inputFile = Examples/Modules/qed/breit_wheeler/inputs_2d
 aux1File = Examples/Modules/qed/breit_wheeler/analysis_core.py
-runtime_params = diag1.format = openpmd
+runtime_params = diag1.format = openpmd diag1.openpmd_backend = h5
 dim = 2
 addToCompileString = QED=TRUE USE_OPENPMD=TRUE
 cmakeSetupOpts = -DWarpX_DIMS=2 -DWarpX_QED=ON -DWarpX_OPENPMD=ON
@@ -1417,7 +1417,7 @@ tolerance = 1.e-14
 buildDir = .
 inputFile = Examples/Modules/qed/breit_wheeler/inputs_3d
 aux1File = Examples/Modules/qed/breit_wheeler/analysis_core.py
-runtime_params = diag1.format = openpmd
+runtime_params = diag1.format = openpmd diag1.openpmd_backend = h5
 dim = 3
 addToCompileString = QED=TRUE USE_OPENPMD=TRUE
 cmakeSetupOpts = -DWarpX_DIMS=3 -DWarpX_QED=ON -DWarpX_OPENPMD=ON