Several MemoryExtensions.LastIndexOfAnyExcept overloads incorrectly document "first occurrence" #136282

Description

The XML documentation for several MemoryExtensions.LastIndexOfAnyExcept<T> overloads contains contradictory wording.

The method summaries correctly state that the methods search for the last index. However, their <returns> sections incorrectly say that the returned index is the index of the first occurrence:

The index in the span of the first occurrence of any value other than those in <paramref name="values"/>.

first occurrence should be changed to last occurrence.

Affected APIs

LastIndexOfAnyExcept<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> values) where T : IEquatable<T>?

LastIndexOfAnyExcept<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> values, IEqualityComparer<T>? comparer = null)

There may be additional overloads containing the same copied wording.

Reproduction Steps

1. Open System.MemoryExtensions in the dotnet/runtime repository.
2. Locate the XML documentation for the following overloads:

LastIndexOfAnyExcept<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> values) where T : IEquatable<T>?

LastIndexOfAnyExcept<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> values, IEqualityComparer<T>? comparer = null)

3. Inspect the <returns> documentation.

Expected behavior

The <returns> documentation should state that the method returns the index of the last occurrence of a value.

Actual behavior

The <returns> documentation incorrectly states that the method returns the index of the first occurrence of a value.

Regression?

No known regression. This appears to be an existing XML documentation error.

Known Workarounds

No response

Configuration

Not configuration-specific. This issue affects the XML documentation in System.MemoryExtensions.

Other information

No response