Fix another memory leak reported in CIFuzz

Fix another memory leak reported in CIFuzz

Direct leak of 2 byte(s) in 1 object(s) allocated from:
    #0 0x4a067d in __interceptor_malloc /src/llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:129:3
    #1 0x57acd9 in CRYPTO_malloc /src/openssl/crypto/mem.c:184:12
    #2 0x57e106 in CRYPTO_strdup /src/openssl/crypto/o_str.c:24:11
    #3 0x5c139f in def_load_bio /src/openssl/crypto/conf/conf_def.c:427:45
    #4 0x56adf5 in NCONF_load_bio /src/openssl/crypto/conf/conf_lib.c:282:12
    #5 0x4d96cf in FuzzerTestOneInput /src/openssl/fuzz/conf.c:38:5
    #6 0x4d9830 in LLVMFuzzerTestOneInput /src/openssl/fuzz/driver.c:28:12
    #7 0x510c23 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) cxa_noexception.cpp
    #8 0x4fc4d2 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:324:6
    #9 0x501f85 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) cxa_noexception.cpp
    #10 0x52ac82 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10
    #11 0x7f15336bf0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16813)