Remove old workaround for toString that was import-leaking in (#2520)

fluffy/network/history/history_network.nim

@@ -24,29 +24,6 @@ logScope:
 
 export accumulator
 
-# This looks like it makes no sense, because it makes no sense. It's a
-# workaround for what seems to be a compiler bug; see here:
-#
-# https://github.com/status-im/nimbus-eth1/pull/1465
-#
-# Without this, the call `error` on a `Result` might give a compiler error for
-# the `Result[BlockHeader, string]` or `Result[seq[BlockHeader], string]` types.
-# The error is due to the `$` for `BlockHeader causing side effects, which
-# appears to be due to the timestamp field, which is of `times.Time` type. Its
-# `$` from the times module has side effects (Yes, silly times). In (my) theory
-# this `$` should not leak here, but it seems to do. To workaround this we
-# introduce this additional `$` call, which appears to work.
-#
-# Note that this also fixes the same error in another module, even when not
-# specifically exporting (no asterisk) the call.
-#
-# If you think this is unnecessary, feel free to try deleting it; if all the
-# tests still pass after deleting it, feel free to leave it out. In the
-# meantime, please just ignore it and go on with your life.
-#
-proc `$`(x: BlockHeader): string =
-  $x
-
 type
   HistoryNetwork* = ref object
     portalProtocol*: PortalProtocol