refactor(compiler): fix Compiler.dialect type hint, remove unneeded…

… `duckdb` compilation rule for `RegexReplace` (#10400)

ibis/backends/sql/compilers/base.py

@@ -522,7 +522,7 @@ def impl(self, op, *, left, right):
 
     @property
     @abc.abstractmethod
-    def dialect(self) -> str:
+    def dialect(self) -> type[sg.Dialect]:
         """Backend dialect."""
 
     @property

ibis/backends/sql/compilers/duckdb.py

@@ -523,9 +523,6 @@ def visit_TimestampNow(self, op):
         """DuckDB current timestamp defaults to timestamp + tz."""
         return self.cast(super().visit_TimestampNow(op), dt.timestamp)
 
-    def visit_RegexReplace(self, op, *, arg, pattern, replacement):
-        return self.f.regexp_replace(arg, pattern, replacement, "g")
-
     def visit_First(self, op, *, arg, where, order_by, include_null):
         if not include_null:
             cond = arg.is_(sg.not_(NULL, copy=False))