refactor: improve code quality (#8751)

* remove unnecessary if

`Array.prototype.some` already returns a boolean so an if to return
true or false is completely unnecessary in this case.

* perf: use count instead of find

When using `count` instead of `findOneBy`, the data is not
unnecessarily loaded.

* remove duplicate null check

The variable is checked for null in the lines above and the function
returns if so. Therefore, it can not be null at this point.

* simplify `getJsonSchema`

Because the assigned value is `null` and the used keys are only
shallow, use of `nestedProperty.set` seems inappropriate. Because the
value is not read, the initial for loop can be replaced by a `for..in`
loop.

Since all keys will be assigned `null`, the condition of the ternary
expression in the nested function will always be true. Therefore the
recursion case will never happen. With this the nested function can be
eliminated.

* remove duplicate condition

The code above already checks `dragging` and returns if it is truthy.
Checking it again later is therefore unnecessary.

To make this more obvious the `return` is removed in favour of using
an if...else construct.

* remove impossible "unknown" time

The `ago` variable will always be a number and all non-negative numbers
are already covered by other cases, the negative case is handled with
`future` so there is no case when `unkown` could be achieved.

locales/ja-JP.yml

@@ -1111,7 +1111,6 @@ _sfx:
   channel: "チャンネル通知"
 
 _ago:
-  unknown: "謎"
   future: "未来"
   justNow: "たった今"
   secondsAgo: "{n}秒前"