Remove serde-migrated tests, because the same test already in serde-de

`test_namespaces` equivalent to `struct_::namespaces`.
`test_forwarded_namespace` has no equivalent, but it was ignored anyway.

New tests will be written during solving #218

Author: Mingun

Cargo.toml

@@ -241,11 +241,6 @@ name = "serde-se"
 required-features = ["serialize"]
 path = "tests/serde-se.rs"
 
-[[test]]
-name = "serde-migrated"
-required-features = ["serialize"]
-path = "tests/serde-migrated.rs"
-
 [[test]]
 name = "serde-issues"
 required-features = ["serialize"]