Add missing descriptors for `SmallFloatType` and `EnumType` #233

Job	Run time
Platform test (7.4)	2m 36s
Platform test (8.0)	3m 1s
Platform test (8.1)	3m 8s
Platform test (8.2)	3m 11s
Platform test (8.3)	2m 59s
Platform test (8.4)	3m 2s
Platform test (8.1, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	2m 28s
Platform test (8.2, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	3m 4s
Platform test (8.3, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	2m 42s
Platform test (8.4, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	3m 11s
	29m 22s

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