Remove MEDIAN_PEER_GROUP as selectable comparison option

[mevionfamos]

Description

The option MEDIAN_PEER_GROUP is redundant, since the median is always displayed anyways (it doesn't change) and should therefore be removed.

Reproduction Steps

1. Navigate to https://www.strompreis.ref.elcom.admin.ch/sunshine/operator/426/costs-and-tariffs?compareWith=10773%2C11%2C105%2C114%2C10000&viewBy=progress&tab=networkCosts
2. Click on Compare with and search for `median
3. Observe the option MEDIAN_PEER_GROUP

Expected Behavior

If we want users to compare both the general median and the peer group median, we should introduce a toggle or add it by default, alongside the swiss median. Otherwise remove this option

Additional Context

• originally reported in Median Behaviour #341

Test Environment

• Ref
• Abn
• Prod