rpk: fix remaining BUILD go_test dep mismatches

Gazelle-generated diff still flagged three test target dep
lists on the previous pass:

- plugin: add //src/go/rpk/pkg/out — list_test.go imports it
- security/secret: same
- transform: drop @in_gopkg_yaml_v3//:yaml_v3 — list_test.go
  no longer imports it after the test rework

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

Author: graham-rp

src/go/rpk/pkg/cli/plugin/BUILD

@@ -27,6 +27,7 @@ go_test(
     embed = [":plugin"],
     deps = [
         "//src/go/rpk/pkg/config",
+        "//src/go/rpk/pkg/out",
         "@com_github_stretchr_testify//require",
     ],
 )

src/go/rpk/pkg/cli/security/secret/BUILD

@@ -32,6 +32,7 @@ go_test(
     embed = [":secret"],
     deps = [
         "//src/go/rpk/pkg/config",
+        "//src/go/rpk/pkg/out",
         "@com_github_stretchr_testify//require",
     ],
 )

src/go/rpk/pkg/cli/transform/BUILD

@@ -50,6 +50,5 @@ go_test(
         "@com_github_stretchr_testify//assert",
         "@com_github_stretchr_testify//require",
         "@com_github_twmb_franz_go//pkg/kgo",
-        "@in_gopkg_yaml_v3//:yaml_v3",
     ],
 )