chore(tool/cmd/migrate): update keep for Go libraries (#4842)

Update keep for Go library bigtable, firestore and pubsub/v2.

For #3618

Author: JoeWang1127

tool/cmd/migrate/go_api.go

@@ -30,13 +30,16 @@ var (
 		"auth/oauth2adapt":  {"internal/version.go"},
 		"batch":             {"apiv1/iam_policy_client.go"},
 		"bigquery":          {"README.md"},
+		"bigtable":          {"README.md"},
 		"compute/metadata":  {"internal/version.go", "README.md"},
 		"containeranalysis": {"apiv1beta1/grafeas/grafeaspb/grafeas.pb.go"},
 		"datacatalog":       {"apiv1/iam_policy_client.go"},
 		"datastream":        {"apiv1/iam_policy_client.go"},
+		"firestore":         {"README.md"},
 		"grafeas":           {"internal/version.go", "README.md"},
 		"profiler":          {"internal/version.go", "README.md"},
 		"pubsub":            {"internal/version.go", "README.md"},
+		"pubsub/v2":         {"README.md"},
 		"root-module":       {"internal/version.go", "README.md"},
 		"run":               {"apiv2/locations_client.go"},
 		"spanner":           {"README.md"},

tool/cmd/migrate/legacylibrarian_test.go

@@ -938,6 +938,7 @@ func TestBuildGoLibraries(t *testing.T) {
 						{Path: "google/bigtable/v2"},
 						{Path: "google/bigtable/admin/v2"},
 					},
+					Keep: []string{"README.md"},
 					Go: &config.GoModule{
 						GoAPIs: []*config.GoAPI{
 							{Path: "google/bigtable/admin/v2", NoMetadata: true, ProtoOnly: true},
@@ -1011,6 +1012,48 @@ func TestBuildGoLibraries(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "firestore keep",
+			input: &MigrationInput{
+				librarianState: &legacyconfig.LibrarianState{
+					Libraries: []*legacyconfig.LibraryState{
+						{
+							ID: "firestore",
+						},
+					},
+				},
+				librarianConfig: &legacyconfig.LibrarianConfig{},
+				repoPath:        "testdata/google-cloud-go",
+				googleapisDir:   "testdata/googleapis",
+			},
+			want: []*config.Library{
+				{
+					Name: "firestore",
+					Keep: []string{"README.md"},
+				},
+			},
+		},
+		{
+			name: "pubsub/v2 keep",
+			input: &MigrationInput{
+				librarianState: &legacyconfig.LibrarianState{
+					Libraries: []*legacyconfig.LibraryState{
+						{
+							ID: "pubsub/v2",
+						},
+					},
+				},
+				librarianConfig: &legacyconfig.LibrarianConfig{},
+				repoPath:        "testdata/google-cloud-go",
+				googleapisDir:   "testdata/googleapis",
+			},
+			want: []*config.Library{
+				{
+					Name: "pubsub/v2",
+					Keep: []string{"README.md"},
+				},
+			},
+		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			got, err := buildGoLibraries(test.input)