C2SoftAomEnc: set AOME_SET_MAX_INTRA_BITRATE_PCT

to 300 for CBR, 450 otherwise. This matches the setting in WebRTC [1]
(where this wrapper's settings are derived from) for CBR and prevents
overshoot in CTS tests that set a low (forced) key frame interval and
use VBR.

[1]: https://webrtc.googlesource.com/src/+/bd42ee87507e8b55a37ec89e7e659a249825f69a/modules/video_coding/codecs/av1/libaom_av1_encoder.cc#289

Bug: 369325415
Test: (komodo) atest \
  MctsMediaCodecTestCases:android.media.codec.cts.VideoCodecTest#testBasic \
  -- \
  --module-arg MctsMediaCodecTestCases:instrumentation-arg:codec-prefix:=c2.android.av1.encoder
Change-Id: Id0dbeda7cfec33ef0fa438a7a2b0453c0c504961