variable_bindings/declare.md: Contradictory statements about uninitialized variables. #1900

It says not initializing a variable when it's declared may lead to use of uninitialized variables, but the sentence after the example says the compiler forbids the use of an uninitialized variable. If the compiler forbids using uninitialized variables, it's not possible to use an uninitialized variable.

The part saying this form is seldom used because it could lead to the use of uninitialized variables should be removed, since it's not possible in Rust.