ci: remove MSAN getrandom syscall workaround

The corresponding workaround will also be dropped in oss-fuzz:
https://github.com/google/oss-fuzz/blob/25946a544856413d31d9cbb3a366a4aef5a8fd60/projects/bitcoin-core/build.sh#L49.

ci/test/06_script_b.sh

@@ -101,14 +101,6 @@ cd "${BASE_BUILD_DIR}/bitcoin-$HOST"
 
 bash -c "./configure --cache-file=../config.cache $BITCOIN_CONFIG_ALL $BITCOIN_CONFIG" || ( (cat config.log) && false)
 
-if [[ ${USE_MEMORY_SANITIZER} == "true" ]]; then
-  # MemorySanitizer (MSAN) does not support tracking memory initialization done by
-  # using the Linux getrandom syscall. Avoid using getrandom by undefining
-  # HAVE_SYS_GETRANDOM. See https://github.com/google/sanitizers/issues/852 for
-  # details.
-  grep -v HAVE_SYS_GETRANDOM src/config/bitcoin-config.h > src/config/bitcoin-config.h.tmp && mv src/config/bitcoin-config.h.tmp src/config/bitcoin-config.h
-fi
-
 if [[ "${RUN_TIDY}" == "true" ]]; then
   MAYBE_BEAR="bear --config src/.bear-tidy-config"
   MAYBE_TOKEN="--"