Fix formulations in label descriptions

Author: flip1995

CONTRIBUTING.md

@@ -315,10 +315,10 @@ an ICE in a popular crate that many other crates depend on. We don't
 want Clippy to crash on your code and we want it to be as reliable as the
 suggestions from Rust compiler errors.
 
-We have prioritization labels and sync-blocker label like below.
+We have prioritization labels and a sync-blocker label, which are described below.
 - [P-low][p-low]: Requires attention (fix/response/evaluation) by a team member but isn't urgent.
 - [P-medium][p-medium]: Should be addressed by a team member until the next sync.
-- [P-high][p-high]: Should be immediately addressed and will require a out-of-cycle sync or a backport.
+- [P-high][p-high]: Should be immediately addressed and will require an out-of-cycle sync or a backport.
 - [L-sync-blocker][l-sync-blocker]: An issue that "blocks" a sync. 
 Or rather: before the sync this should be addressed,
 e.g. by removing a lint again, so it doesn't hit beta/stable.