enable UTF-8 icons for WSL

conhost.exe supports UTF-8 nowadays, even though there is no font fallback and your
font needs to have the appropriate glyphs (DejaVu works, for example).
The new "Windows Terminal" application has a revamped font renderer and just works.

mitmproxy/tools/console/common.py

@@ -95,7 +95,7 @@ def fcol(s, attr):
     )
 
 
-if urwid.util.detected_encoding and not IS_WSL:
+if urwid.util.detected_encoding:
     SYMBOL_REPLAY = u"\u21ba"
     SYMBOL_RETURN = u"\u2190"
     SYMBOL_MARK = u"\u25cf"