test: remove unused EncodeDecimal from test framework util

Author: PastaPastaPasta

test/functional/test_framework/util.py

@@ -228,12 +228,6 @@ def check_json_precision():
         raise RuntimeError("JSON encode/decode loses precision")
 
 
-def EncodeDecimal(o):
-    if isinstance(o, Decimal):
-        return str(o)
-    raise TypeError(repr(o) + " is not JSON serializable")
-
-
 def count_bytes(hex_string):
     return len(bytearray.fromhex(hex_string))