Ignore androidx annotation auto-update from Dependabot

androidx annotation brings higher Kotlin dependency than we expect, and
it is in core modules' dependency list, so we need to avoid its
auto-update and update it based on our demand manually.

Signed-off-by: utzcoz <utzcoz@outlook.com>

.github/dependabot.yml

@@ -17,3 +17,5 @@ updates:
        # don't auto update nativeruntime-dist-compat since it needs
        # to be updated with code changes together
        - dependency-name: "org.robolectric:nativeruntime-dist-compat"
+       # don't auto update androidx-annotation since it brings higher Kotlin dependency
+       - dependency-name: "androidx.annotation:annotation"