license: allow fish's own license identifiers

The newly added `cargo deny check licenses` command complains about the
licenses added in this commit not being explicitly allowed, so add them
to the config here. There is no intended change in semantics.

Closes #12097

deny.toml

@@ -7,8 +7,10 @@ allow = [
     "BSD-3-Clause",
     "BSL-1.0",
     "GPL-2.0",
+    "GPL-2.0-only",
     "ISC",
     "LGPL-2.0",
+    "LGPL-2.0-or-later",
     "MIT",
     "MPL-2.0",
     "PSF-2.0",