Tooltip description for saddle attribute modifier slot is not translated

Attribute modifier slots have an associated message in the key format item.modifiers.<slot>, which is shown when listing the attribute modifiers associated with a given slot on an item stack. However, the item.modifiers.saddle translation is missing for the saddle equipment slot which can be targeted by attribute modifiers.

Steps to reproduce

1. Run the following command:

/give @s saddle[minecraft:attribute_modifiers=[{operation:"add_multiplied_base",id:"embiggen",type:"scale",amount:0.3,slot:saddle}]]

2. Observe that the tooltip contains the line item.modifiers.saddle

Expected outcome

The tooltip of an item stack with a saddle attribute modifier would include something like 'When on Back:' or similar.

Actual outcome

The tooltip of an item stack with a saddle attribute modifier includes the untranslated text 'item.modifiers.saddle'.