Fix 3.10's supported features (#2614)

src/black/mode.py

@@ -112,6 +112,15 @@ class Feature(Enum):
         Feature.POS_ONLY_ARGUMENTS,
     },
     TargetVersion.PY310: {
+        Feature.UNICODE_LITERALS,
+        Feature.F_STRINGS,
+        Feature.NUMERIC_UNDERSCORES,
+        Feature.TRAILING_COMMA_IN_CALL,
+        Feature.TRAILING_COMMA_IN_DEF,
+        Feature.ASYNC_KEYWORDS,
+        Feature.ASSIGNMENT_EXPRESSIONS,
+        Feature.RELAXED_DECORATORS,
+        Feature.POS_ONLY_ARGUMENTS,
         Feature.PATTERN_MATCHING,
     },
 }