Turn off UMF_DEVELOPER_MODE in the Valgrind job of Nightly CI build

UMF_DEVELOPER_MODE turns on various debug checks that
should be turned off during valgrind tests.

Signed-off-by: Lukasz Dorau <lukasz.dorau@intel.com>

Author: ldorau

.github/workflows/nightly.yml

@@ -93,7 +93,7 @@ jobs:
         -B ${{github.workspace}}/build
         -DCMAKE_BUILD_TYPE=Debug
         -DUMF_FORMAT_CODE_STYLE=OFF
-        -DUMF_DEVELOPER_MODE=ON
+        -DUMF_DEVELOPER_MODE=OFF
         -DUMF_BUILD_LIBUMF_POOL_JEMALLOC=ON
         -DUMF_BUILD_LEVEL_ZERO_PROVIDER=OFF
         -DUMF_BUILD_CUDA_PROVIDER=OFF