Add rustdoc team to rust-forge and triagebot maintenance

Author: GuillaumeGomez

repos/rust-lang/rust-forge.toml

@@ -17,6 +17,7 @@ libs = "maintain"
 libs-api = "maintain"
 edition = "maintain"
 release = "maintain"
+rustdoc = "maintain"
 triagebot = "maintain"
 
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