fix(android): remove pre-2.0 build: section from detekt config

detekt 2.0 removed the top-level `build:` key:

  Property 'build' is misspelled or does not exist. Allowed properties:
  [comments, complexity, config, console-reports, coroutines,
   empty-blocks, exceptions, naming, performance, potential-bugs,
   processors, style].

The `build.maxIssues = 0` setting we had moved to the Gradle plugin DSL
(`failOnSeverity` option, defaults to Error). Emptied the YAML; rely on
detekt defaults via `buildUponDefaultConfig = true` until we have
specific rule overrides to write.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/config/detekt.yml

@@ -1,3 +1,10 @@
-# Minimal detekt config. Default rules apply via `buildUponDefaultConfig`.
-build:
-  maxIssues: 0
+# Empty detekt config — relies on defaults via `buildUponDefaultConfig = true`
+# in the :app detekt {} block. Per-rule overrides go here as needed:
+#
+#   style:
+#     MagicNumber:
+#       active: false
+#
+# The pre-2.0 `build: maxIssues: 0` top-level was removed; failure
+# threshold is configured via the Gradle DSL's `failOnSeverity` option
+# instead (defaults to Error).