clippy: remove matthiaskrgr from reviewer group

I don't have the capacity to work a lot on clippy right now.

Author: matthiaskrgr

highfive/configs/rust-lang/rust-clippy.json

@@ -1,11 +1,11 @@
 {
     "groups": {
-        "all": ["@ebroto", "@flip1995", "@Manishearth", "@matthiaskrgr", "@phansch"]
+        "all": ["@ebroto", "@flip1995", "@Manishearth", "@phansch"]
     },
     "dirs": {
         ".github": ["@flip1995"],
         "clippy_dev": ["@phansch"]
     },
     "contributing": "https://github.com/rust-lang/rust-clippy/blob/master/CONTRIBUTING.md",
     "new_pr_labels": ["S-waiting-on-review"]
-}
+}