Update to NDK r26.

r23 is no longer used by Kleaf.
Bug: 321898888

Change-Id: I846de948e209a53c6996618016dcf4bf1b2dd5cd
diff --git a/default.xml b/default.xml
index 3702fdc..4640448 100644
--- a/default.xml
+++ b/default.xml
@@ -17,7 +17,7 @@
   <project path="prebuilts/bazel/linux-x86_64" name="platform/prebuilts/bazel/linux-x86_64" clone-depth="1" />
   <project path="prebuilts/bazel/common" name="platform/prebuilts/bazel/common" clone-depth="1" />
   <project path="prebuilts/jdk/jdk11" name="platform/prebuilts/jdk/jdk11" revision="main-kernel" clone-depth="1" />
-  <project path="prebuilts/ndk-r23" name="toolchain/prebuilts/ndk/r23" clone-depth="1" />
+  <project path="prebuilts/ndk-r26" name="toolchain/prebuilts/ndk/r26" clone-depth="1" />
   <project path="external/bazel-skylib" name="platform/external/bazel-skylib" />
   <project path="build/bazel_common_rules" name="platform/build/bazel_common_rules" />
   <project path="external/stardoc" name="platform/external/stardoc" />