recover dropped content + edits

[mairaw]

PR #3055 somehow dropped this content

Recovering that + removing we from the remarks text

[ahsonkhan]

From #2729, the wording was modified:

https://github.com/dotnet/dotnet-api-docs/pull/2729/files#diff-329e2957d7afa212df1c2d8a57ae415aR266

i.e.
https://github.com/carlossanlop/dotnet-api-docs/blob/acbc62c141fcdcd210f630f019edf198a6d5a48d/xml/System/Range.xml#L265-L281

      <Docs>
        <param name="length">A positive integer that represents the length of the collection that the range will be used with.</param>
        <summary>Returns a <see cref="T:System.Range.OffsetAndLength" /> instance with the starting offset and length of a range.</summary>
        <returns>The starting offset and length of the range.</returns>
        <remarks>
          <format type="text/markdown">
            <![CDATA[
## Remarks
For performance reasons, this method does't validate `length` to ensure that it is not negative. It does ensure that `length` is within the current `Range` instance. 
            ]]>
          </format>
        </remarks>
        <exception cref="T:System.ArgumentOutOfRangeException"><paramref name="length" /> is outside the bounds of the current range. </exception>
      </Docs>

[mairaw]

Thanks @ahsonkhan. @rpetrusha please check which version you prefer. The old or the one in this PR which is a mix of the current + old.

[rpetrusha]

I prefer the one in the PR, which is much clearer, @mairaw.

[rpetrusha]

LGTM.