cargo deny warning due to deprecated license expression

[Skgland]

GPL-3.0 is deprecated in favor of GPL-3.0-only see the deprecation warning in https://spdx.org/licenses/GPL-3.0.html

also / is deprecated in favor of OR ¹²

warning[parse-error]: error parsing SPDX license expression
   ┌─ C:\Users\<user>\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\unescaper-0.1.6\Cargo.toml:31:12
   │
31 │ license = "GPL-3.0/MIT"
   │            ─────── a deprecated license identifier was used
   │
   ├ unescaper v0.1.6

Footnotes

1. see footnote https://doc.rust-lang.org/cargo/reference/manifest.html#footnote-slash ↩

2. https://github.com/rust-lang/cargo/issues/2039#issuecomment-3172067095 ↩