Remove allow-multiple-definitions flag.

This is no longer necessary as static linkage in Rust has been fixed.

Bug: 254469782
Test: m aconfig_storage_write_api.test.cpp
Change-Id: I6b8b36882aa521eb0412fb7da03a5eec94df81d4

tools/aconfig/aconfig_storage_write_api/tests/Android.bp

@@ -38,8 +38,7 @@ cc_test {
         "device-tests",
         "general-tests",
     ],
-    ldflags: ["-Wl,--allow-multiple-definition"],
-        generated_headers: [
+    generated_headers: [
         "cxx-bridge-header",
         "libcxx_aconfig_storage_read_api_bridge_header",
     ],