MPEG4Writer: Fix hvcC CSD size check

Replace the mIsHeif check with the mIsHeic. The mIsHeif is true
for avif and av1C CSD is always less than 23 bytes. This change
ensures the minimum size check only for hvcC.

Flag: EXEMPT BUGFIX

Bug: 348525643
Bug: 347125598

Test: ./libstagefright_writer_fuzzer
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:3b59e624d2e88886c7c6127ecd7a27cdcb46ea84
Merged-In: Ieae5f423b7c4a08721c97250c76a11050099a10e
Change-Id: Ieae5f423b7c4a08721c97250c76a11050099a10e