Add missing descriptors for `SmallFloatType` and `EnumType` #232

Job	Run time
Platform test (7.4)	3m 5s
Platform test (8.0)	3m 4s
Platform test (8.1)	2m 47s
Platform test (8.2)	2m 49s
Platform test (8.3)	2m 36s
Platform test (8.4)	2m 37s
Platform test (8.1, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	2m 43s
Platform test (8.2, doctrine/orm:^3.0 doctrine/dbal:^4.0 carbonphp/carbon-doctrine-types:^3 gedmo...	2m 55s
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...	2m 45s
	28m 3s

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