Expenses Handbook: Increase reimbursable ergonomic chair price range

Why is this change being made?

Under the guideline values table for office hardware in the expenses page, the current average listed for ergonomic chairs seems to be targeting the low-end part of the market, even though it's recognised as top priority equipment. This MR proposes increasing the the listed reimbursable and average amounts to also cover mid-range chairs, and better support folks that might require high-end ones.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
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