Can the container used to create a buffer be `const`?

### Specification Version

SYCL 2020 (Revision 11)

### Section Number(s)

Section 4.7.2.1. Constructors, https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#api:buffer-ctor-container.

### Issue Description

This section includes the following two sentences:

1. The return type of `std::data(container)` is convertible to `T*`.
2. Data is written back to container before the completion of buffer destruction if the return type of `std::data(container)` is not `const`.

The "is not `const`" at the end of the second sentence is confusing. If the return type is `const`, this would violate constraint (1) since it wouldn't be convertible to `T*`. It seems the constraint should instead be that `std::data(container)` is convertible to `const T *`.

### Code Example (Optional)

Relevant example is in https://github.com/0x12CC/ProtoSYCL/pull/3.

Read SYCL 2020 Section 4.7.2.1 and compare its two sentences about std::data(container), const, and conversion to T*. Review the relevant example in the ProtoSYCL pull request linked in the issue. Done means the specification wording unambiguously resolves the apparent conflict between the two constraints.

Written by the indexing model from the issue text.