[pylint] fix global-variable-not-assigned issues

If there is no write access, there is no need for global.  Remove global
statement if there is no assignment.

global-variable-not-assigned:
  Using global for names but no assignment is done Used when a variable is
  defined through the "global" statement but no assignment to this variable is
  done.

In Pylint 2.11 the global-variable-not-assigned checker now catches global
variables that are never reassigned in a local scope and catches (reassigned)
functions [1][2]

[1] https://pylint.pycqa.org/en/latest/whatsnew/2.11.html
[2] https://github.com/PyCQA/pylint/issues/1375

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/search/processors/online_currency.py

@@ -18,7 +18,6 @@ def normalize_name(name):
     return unicodedata.normalize('NFKD', name).lower()
 
 def name_to_iso4217(name):
-    global CURRENCIES  # pylint: disable=global-statement
     name = normalize_name(name)
     currency = CURRENCIES['names'].get(name, [name])
     if isinstance(currency, str):
@@ -26,7 +25,6 @@ def name_to_iso4217(name):
     return currency[0]
 
 def iso4217_to_name(iso4217, language):
-    global CURRENCIES  # pylint: disable=global-statement
     return CURRENCIES['iso4217'].get(iso4217, {}).get(language, iso4217)
 
 class OnlineCurrencyProcessor(OnlineProcessor):