contrib: aom: update to 3.9.1

2024-06-05 v3.9.1
  This release includes several bug fixes. This release is ABI
  compatible with the last release. See
  https://aomedia.googlesource.com/aom/+log/v3.9.0..v3.9.1 for all the
  commits in this release.
  - Bug Fixes
    * aomedia:2754, aomedia:3567: Ensure thread stack size is at least
      256 KB
    * b:330639949, oss-fuzz:68195: Increase scaling in linsolve_wiener
    * Fix high target data rate overflow.
    * aomedia:3509: Fix two UBSan errors in av1_rc_update_framerate()
    * aomedia:3382, chromium:339877165: update codec config after
      svc/scale controls (CVE-2024-5493)
    * aomedia:3561: libaom-3.8.2 armv7 Android build failed
    * aomedia:3571: {,highbd_}intrapred_neon.c: Avoid over-reads in z1
      and z3 preds
    * aomedia:3578: libaom-3.9.0 undefined reference to
      `aom_sub_pixel_variance16xh_ssse3'
    * aomedia:3579: Use round for RC calculations in cyclic_refresh
    * aomedia:3580: Allow g_timebase.num to be greater than
      g_timebase.den
    * oss-fuzz:68774: libaom:av1_dec_fuzzer: Segv on unknown address in
      od_ec_dec_init
    * Arm SVE build fixes.
    * av1_block_error_lp_neon: fix block_size param type
    * av1_block_error_lp_sve: fix block_size param type