Reword best weight and volume metrics

Previously we didn't have a period selector,
so the description was "Best weight per day"
and "Best volume per day". Now that the user
can also select the period (daily, monthly, yearly)
it doesn't make sense to label them as "per day".

metrics.ts

@@ -1,5 +1,5 @@
 export enum Metrics {
-  Weight = 'Best weight per day',
-  Volume = 'Volume per day',
+  Weight = 'Best weight',
+  Volume = 'Volume',
   OneRepMax = 'One rep max',
 }