[Docs][BottomSheet][SideSheet] Difference between spec and implementation

Update the docs or the implementation.

BottomSheet

Description:
https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/bottomsheet/res/values/styles.xml#L73:

<item name="backgroundTint">@macro/m3_comp_sheet_bottom_docked_container_color</item>

https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/bottomsheet/res/values/tokens.xml#L24:

<macro name="m3_comp_sheet_bottom_docked_container_color">?attr/colorSurfaceContainerLow</macro>

https://m3.material.io/components/bottom-sheets/specs:

(3) Surface

Expected behavior:
https://m3.material.io/components/bottom-sheets/specs:

(3) Surface container low

SideSheet

Description:
https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/sidesheet/res/values/styles.xml#L49:

<item name="backgroundTint">@macro/m3_comp_sheet_side_docked_modal_container_color</item>

https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/sidesheet/res/values/tokens.xml#L24:

<macro name="m3_comp_sheet_side_docked_modal_container_color">?attr/colorSurfaceContainerLow</macro>

https://m3.material.io/components/side-sheets/specs:

Modal side sheet color

(3) Surface

Expected behavior:
https://m3.material.io/components/side-sheets/specs:

(3) Surface container low

Compare the BottomSheet and SideSheet backgroundTint entries and token definitions in their linked styles.xml and tokens.xml files with the corresponding Material 3 specification pages. First determine whether the specification or implementation is authoritative; done means the documented surface color and the component behavior agree for both sheets.