git: gpg sign tags with signing.signByDefault set

The `tag.gpgSign` config option was added in Git 2.23.0 and seems like
it should be set in addition to `commit.gpgSign` when
`programs.git.signing.signByDefault` is enabled

tests/modules/programs/git/git-expected.conf

@@ -43,6 +43,9 @@
 [interactive]
 	diffFilter = "@delta@/bin/delta --color-only"
 
+[tag]
+	gpgSign = true
+
 [user]
 	email = "user@example.org"
 	name = "John Doe"

tests/modules/programs/git/git-with-signing-key-id-expected.conf

@@ -4,6 +4,9 @@
 [gpg]
 	program = "path-to-gpg"
 
+[tag]
+	gpgSign = true
+
 [user]
 	email = "user@example.org"
 	name = "John Doe"

tests/modules/programs/git/git-without-signing-key-id-expected.conf

@@ -4,6 +4,9 @@
 [gpg]
 	program = "path-to-gpg"
 
+[tag]
+	gpgSign = true
+
 [user]
 	email = "user@example.org"
 	name = "John Doe"