Fix JNI errors in autofill_assistant with isolated splits

I forgot to add split_name to this generate_jni call.

Bug: 1155277
Change-Id: I06d56ad42ffbc6afda34e64ee8f6037933f7b3ec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2573160
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Clark DuVall <cduvall@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833602}

chrome/android/features/autofill_assistant/BUILD.gn

@@ -228,6 +228,7 @@ generate_jni("jni_headers") {
     "java/src/org/chromium/chrome/browser/autofill_assistant/user_data/AssistantCollectUserDataNativeDelegate.java",
     "java/src/org/chromium/chrome/browser/autofill_assistant/user_data/AssistantDateTime.java",
   ]
+  split_name = "autofill_assistant"
 }
 
 generate_jni("test_support_jni_headers") {