fix: deflake //rs/nns/sns-wasm:sns-wasm_integration_test_tests/upgrade_sns_instance by increasing timeout (#9795)

As show by:
```
bazel run //ci/githubstats:query -- last --non_success --month //rs/nns/sns-wasm:sns-wasm_integration_test_tests/upgrade_sns_instance
```
that test frequently times out. To fix it we increase the timeout of the
test suite from 5 to 15 minutes.

Author: basvandijk

rs/nns/sns-wasm/BUILD.bazel

@@ -121,6 +121,9 @@ rust_test(
 
 rust_ic_test_suite_with_extra_srcs(
     name = "sns-wasm_integration_test",
+    # //rs/nns/sns-wasm:sns-wasm_integration_test_tests/upgrade_sns_instance
+    # frequently times out on CI so we give the test suite more time:
+    timeout = "long",
     srcs = glob(
         ["tests/**/*.rs"],
         exclude = [