gtk4-macros: depend on proc-macro2 1.0.100

This version stablilised `Span::local_file()` which we now need. Without
specifying the version, apps or other libraries might not have a new enough
version and they might be able to compile.

Author: carlosmn

gtk4-macros/Cargo.toml

@@ -23,7 +23,7 @@ blueprint = []
 [dependencies]
 quick-xml = {version = "0.39", optional = true}
 proc-macro-crate = "3.3"
-proc-macro2 = { version = "1.0", features = ["span-locations"] }
+proc-macro2 = { version = "1.0.100", features = ["span-locations"] }
 quote = "1.0"
 syn = {version = "2.0", features = ["full"]}