Update the license to GPL-3.0

Author: OmegaTymbJIep

Cargo.toml

@@ -2,7 +2,7 @@
 name    = "taprootized-atomic-swaps"
 version = "0.1.0"
 edition = "2021"
-license = "MIT"
+license = "GPL-3.0"
 
 [dependencies]
 eyre = { version = "0.6.11" }