patch 9.0.2119: remove dead-condition in ex_class

patch 9.0.2119: remove dead-condition in ex_class

Problem:  remove dead-condition in ex_class()
Solution: remove the extra condition

The variable is_class must be true once we reach the

,----
| else if (has_static)
`----

in line 1750, because we break out earlier if is_class is false in line
1598 of vim9class.c. And once 'has_static = TRUE', we must be in a
class and there fore is_class is true.

Signed-off-by: Christian Brabandt <cb@256bit.org>