rust-lang/rust: Remove outdated entries

Author: petrochenkov

highfive/configs/rust-lang/rust.json

@@ -2,7 +2,6 @@
     "groups": {
         "all": [],
         "compiler": ["@eddyb", "@petrochenkov", "@estebank", "@varkor", "@lcnr", "@matthewjasper", "@davidtwco", "@ecstatic-morse", "@oli-obk"],
-        "syntax": ["@petrochenkov", "@eddyb"],
         "libs": ["@sfackler", "@dtolnay", "@JoshTriplett", "@hanna-kruppe", "@withoutboats", "@cramertj", "@shepmaster", "@Mark-Simulacrum", "@kennytm", "@LukasKalbertodt", "@KodrAus"],
         "infra-ci": ["@Mark-Simulacrum", "@kennytm", "@pietroalbini"],
         "rustdoc": ["@steveklabnik", "@GuillaumeGomez", "@ollie27"]
@@ -17,18 +16,13 @@
         "src/doc":                  ["doc"],
         "src/etc":                  ["@Mark-Simulacrum"],
         "src/liballoc":             ["libs"],
-        "src/libarena":             ["libs"],
         "src/libcore":              ["libs"],
-        "src/libfmt_macros":        ["libs"],
-        "src/libgraphviz":          ["@pnkfelix"],
         "src/libpanic_abort":       ["libs"],
         "src/libpanic_unwind":      ["libs"],
         "src/libproc_macro":        ["@petrochenkov"],
         "src/librustc":             ["compiler"],
         "src/librustdoc":           ["rustdoc"],
-        "src/libserialize":         ["libs", "@erickt"],
         "src/libstd":               ["libs"],
-        "src/libsyntax":            ["syntax"],
         "src/libterm":              ["libs"],
         "src/libtest":              ["libs"],
         "src/llvm-project":         ["@cuviper"],