Remove the cmake option XAPP_MULTILANGUAGE from all Dockerfiles

The FlexRIC main CMakeLists.txt sets XAPP_MULTILANGUAGE to OFF by default.
Related commit ID: https://gitlab.eurecom.fr/mosaic5g/flexric/-/commit/637f718c3241f2f9ee809ecbd8a67ccb88575e65

docker/Dockerfile.build.rhel9

@@ -41,8 +41,7 @@ RUN /bin/sh oaienv && \
     scl enable gcc-toolset-13 "\
     CXXFLAGS='-Werror -fstack-protector-strong' CFLAGS='-Werror -fstack-protector-strong' ./build_oai -c --ninja \
       --eNB --gNB --RU --UE --nrUE \
-      --build-e2 --cmake-opt -DXAPP_MULTILANGUAGE=OFF --cmake-opt \
-      -DKPM_VERSION=$KPM_VERSION --cmake-opt -DE2AP_VERSION=$E2AP_VERSION \
+      --build-e2 --cmake-opt -DKPM_VERSION=$KPM_VERSION --cmake-opt -DE2AP_VERSION=$E2AP_VERSION \
       --build-lib 'telnetsrv enbscope uescope nrscope' \
       --build-tool-opt -k10 \
       -w USRP -t Ethernet \
@@ -57,7 +56,6 @@ RUN mkdir -p openair2/E2AP/flexric/build && \
     cd openair2/E2AP/flexric/build && \
     scl enable gcc-toolset-13 "\
     cmake -GNinja -DCMAKE_BUILD_TYPE=Release \
-          -DXAPP_MULTILANGUAGE=OFF \
           -DKPM_VERSION=$KPM_VERSION \
           -DE2AP_VERSION=$E2AP_VERSION .. &&\
     ninja && \