fix(clickhouse): Remove CURRENT_TIMESTAMP from NO_PAREN_FUNCTIONS (#4079)

Author: VaggelisD

sqlglot/dialects/clickhouse.py

@@ -403,6 +403,9 @@ class Parser(parser.Parser):
         NO_PAREN_FUNCTION_PARSERS = parser.Parser.NO_PAREN_FUNCTION_PARSERS.copy()
         NO_PAREN_FUNCTION_PARSERS.pop("ANY")
 
+        NO_PAREN_FUNCTIONS = parser.Parser.NO_PAREN_FUNCTIONS.copy()
+        NO_PAREN_FUNCTIONS.pop(TokenType.CURRENT_TIMESTAMP)
+
         RANGE_PARSERS = {
             **parser.Parser.RANGE_PARSERS,
             TokenType.GLOBAL: lambda self, this: self._match(TokenType.IN)

tests/dialects/test_clickhouse.py

@@ -515,6 +515,7 @@ def test_clickhouse(self):
         )
         self.validate_identity("SELECT TRIM(TRAILING ')' FROM '(   Hello, world!   )')")
         self.validate_identity("SELECT TRIM(LEADING '(' FROM '(   Hello, world!   )')")
+        self.validate_identity("current_timestamp").assert_is(exp.Column)
 
     def test_clickhouse_values(self):
         values = exp.select("*").from_(