GNUMakefile: disable tab expansion for 'make format'

This was only needed for initial migration.

GNUmakefile

@@ -517,7 +517,7 @@ update: .FORCE
 
 format: .FORCE
 	PATH="../lib/${OS_NCASE}/llvm/bin/:$(PATH)" \
-		python3 source/tools/utils_maintenance/clang_format_paths.py --expand-tabs $(PATHS)
+		python3 source/tools/utils_maintenance/clang_format_paths.py $(PATHS)
 
 
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