fix(tests): remove invalid-type cases from ValidateBlockHeight tests

[AdamuAbba]

Description

• commit - 70f3518
  • Remove 123.5 (double) and std::string assertions from ValidateBlockHeight test:

    • Since type rejection is a compiler concern, not runtime logic so invalid types should fail to compile, not return error strings.

      

    • removing both validate_block_height(123.5) and validate_block_height(std::string{"100"}) assertions allows ValidateBlockHeight test to pass once a student provides a solution accounting for runtime logic tests (negative values, out-of-range, etc), without changing the validate_block_height function parameter type.

      

[bartoli]

Not sure about removing the decimal test, but surely, adding an overload taking a string just to return that strings are not supported is strange