Fix up casing in board argument

Author: jmartinez-silabs

scripts/build/testdata/dry_run_efr32-brd4187c-light-rpc-no-version.txt

@@ -2,7 +2,7 @@
 cd "{root}"
 
 # Generating efr32-brd4187c-light-rpc-no-version
-gn gen --check --fail-on-unused-args --export-compile-commands --root={root}/examples/lighting-app/silabs '--args=silabs_board="brd4187c" is_debug=false import("//with_pw_rpc.gni") efr32_sdk_root="TEST_GSDK_ROOT" openthread_root="TEST_GSDK_ROOT/util/third_party/openthread" wiseconnect_sdk_root="TEST_WISECONNECT_SDK_ROOT" wifi_sdk_root="TEST_WIFI_SDK_ROOT"' {out}/efr32-brd4187c-light-rpc-no-version
+gn gen --check --fail-on-unused-args --export-compile-commands --root={root}/examples/lighting-app/silabs '--args=silabs_board="BRD4187C" is_debug=false import("//with_pw_rpc.gni") efr32_sdk_root="TEST_GSDK_ROOT" openthread_root="TEST_GSDK_ROOT/util/third_party/openthread" wiseconnect_sdk_root="TEST_WISECONNECT_SDK_ROOT" wifi_sdk_root="TEST_WIFI_SDK_ROOT"' {out}/efr32-brd4187c-light-rpc-no-version
 
 # Building efr32-brd4187c-light-rpc-no-version
 ninja -C {out}/efr32-brd4187c-light-rpc-no-version