servo: Merge #15774 - Remove tidy exceptions for serde and syn (from mbrubeck:tidy); r=nox

r? @nox

Source-Repo: https://github.com/servo/servo
Source-Revision: 79028427304b1ca3df8fe391de98ab4fcd34087e

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 0ec96cf248748cccb91a3b20fe0bdb4cf9b32225

servo/servo-tidy.toml

@@ -31,7 +31,7 @@ num = []
 
 [ignore]
 # Ignored packages with duplicated versions
-packages = ["byteorder", "serde_codegen_internals", "syn"]
+packages = ["byteorder"]
 # Files that are ignored for all tidy and lint checks.
 files = [
   # Generated and upstream code combined with our own. Could use cleanup