remove Decoration.name_expression again because Decoration.name is sufficient

[NiklasRosenstein]

Having just the Decoration.name field should be enough if the name can also be an expression.

Code	Decorator.name	Decorator.args	Notes
@property	"property"	null
@functools.lru_cache(max_size=10)	"functools.lru_cache"	["max_size=10"]
@dec['name']	"dec['name']"	null	since Python 3.9
@(decorators().name)(a, b=c)	"(decorators().name)"	["a", "b=c"]	since Python 3.9

[NiklasRosenstein]

With #48, it should be

Code	Decorator.name	Decorator.arglist	Notes
@property	"property"	null
@functools.lru_cache(max_size=10)	"functools.lru_cache"	["max_size=10"]
@dec['name']	"dec['name']"	null	since Python 3.9
@(decorators().name)(a, b=c)	"(decorators().name)"	["a", "b=c"]	since Python 3.9

(Just renamed Decoration.args to Decoration.arglist)