Drop redundant resolver setting for 2021 edition

.config/hakari.toml

@@ -10,6 +10,8 @@ dep-format-version = "2"
 # Hakari works much better with the new feature resolver.
 # For more about the new feature resolver, see:
 # https://blog.rust-lang.org/2021/03/25/Rust-1.51.0.html#cargos-new-feature-resolver
+# Have to keep the resolver still here since hakari requires this field,
+# despite it's now the default for 2021 edition & cargo.
 resolver = "2"
 
 # Add triples corresponding to platforms commonly used by developers here.

Cargo.toml

@@ -11,7 +11,6 @@ members = [
     "zenith_metrics",
     "zenith_utils",
 ]
-resolver = "2"
 
 [profile.release]
 # This is useful for profiling and, to some extent, debug.

pre-commit.py

@@ -29,7 +29,7 @@ def colorify(
 
 
 def rustfmt(fix_inplace: bool = False, no_color: bool = False) -> str:
-    cmd = "rustfmt --edition=2018"
+    cmd = "rustfmt --edition=2021"
     if not fix_inplace:
         cmd += " --check"
     if no_color: