rename dav1d -> libdav1d

* Google has added option for using libdav1d for AV1 software decoding
  in future Android versions (excellent idea wherever they got it ;)).
* Rename the repo to follow AOSP naming convention.

manifest_brcm_rpi4.xml

@@ -35,9 +35,9 @@
   <project path="external/libyuv_chromium" name="raspberry-vanilla/android_external_libyuv_chromium" remote="github" revision="android-14.0" />
 
   <!-- FFmpeg -->
-  <project path="external/dav1d" name="raspberry-vanilla/android_external_dav1d" remote="github" revision="android-14.0" />
   <project path="external/ffmpeg" name="raspberry-vanilla/android_external_ffmpeg" remote="github" revision="android-14.0" />
   <project path="external/ffmpeg_codec2" name="raspberry-vanilla/android_external_ffmpeg_codec2" remote="github" revision="android-14.0" />
+  <project path="external/libdav1d" name="raspberry-vanilla/android_external_libdav1d" remote="github" revision="android-14.0" />
   <project path="external/libudev-zero" name="raspberry-vanilla/android_external_libudev-zero" remote="github" revision="android-14.0" />
 
   <!-- Graphics -->