kokoro: use NDK r29 (KhronosGroup#6669)

Bug: crbug.com/507146491

Author: dneto0

kokoro/scripts/linux/build-docker.sh

@@ -195,7 +195,7 @@ elif [ $TOOL = "cmake-dxc-smoketest" ]; then
 
 elif [ $TOOL = "cmake-android-ndk" ]; then
   using cmake-3.31.2
-  using ndk-r27c
+  using ndk-r29
   using ninja-1.10.0
 
   clean_dir "$ROOT_DIR/build"
@@ -215,7 +215,7 @@ elif [ $TOOL = "cmake-android-ndk" ]; then
   ninja
   echo $(date): Build completed.
 elif [ $TOOL = "android-ndk-build" ]; then
-  using ndk-r27c
+  using ndk-r29
 
   clean_dir "$ROOT_DIR/build"
   cd "$ROOT_DIR/build"