Enforce trybuild >= 1.0.108

Older versions produce slightly differently normalized output
when run against 1.90.0+ Rust compiler.

Author: dtolnay

tests/ui/Cargo.toml

@@ -12,4 +12,4 @@ path = "compiletest.rs"
 [dev-dependencies]
 proc-macro2 = { path = "../.." }
 rustversion = "1.0"
-trybuild = { version = "1.0.49", features = ["diff"] }
+trybuild = { version = "1.0.108", features = ["diff"] }