datalake: suppress alignment errors from Arrow

When reading Parquet files, the Arrow library reads int32s from
unaligned memory. After upgrading to Clang 18 we started getting
warnings about this when testing locally and errors in CI. This is safe
to suppress: the read code path is only used in tests.

ubsan_suppressions.txt

@@ -3,3 +3,4 @@ nonnull-attribute:aead.c
 alignment:crc32c_arm64.cc
 function:openssl/*.c
 function:openssl-fips/*.c
+alignment:arrow/util/ubsan.h