fstream: reformat the doxygen comment of make_file_input_stream() #187

Job	Run time
Test with DPDK enabled / test	22m 39s
Test (clang++, C++20, dev) / test	17m 6s
Test (clang++, C++20, debug) / test	15m 29s
Test with C++20 modules enabled / test	8m 35s
Test (clang++, C++20, release) / test	15m 25s
Test (clang++, C++23, debug) / test	14m 13s
Test (clang++, C++23, release) / test	19m 11s
Test (clang++, C++23, dev) / test	16m 52s
Test (g++, C++20, debug) / test	18m 59s
Test (g++, C++20, dev) / test	13m 38s
Test (g++, C++20, release) / test	17m 3s
Test (g++, C++23, dev) / test	12m 52s
Test (g++, C++23, release) / test	16m 58s
Test (g++, C++23, debug) / test	19m 6s
	3h 48m 6s

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