Update Python docs

[lorddaedra]

Update Python docs to use these aliases

• Update docs for applyAddOn:
• replace client.applied_add_ons.create(...)
• to client.add_ons.apply(...)
• Update docs for findAllBillableMetricGroups:
• replace client.groups.find_all(...)
• to client.billable_metrics.find_all_groups(...)
• Update docs for applyCoupon:
• replace client.applied_coupons.create(...)
• to client.coupons.apply(...)
• Update docs for findAllAppliedCoupons:
• replace client.applied_coupons.find_all(...)
• to client.coupons.find_all_applied(...)
• Update docs for deleteAppliedCoupon:
• replace client.applied_coupons.destroy(...)
• to client.coupons.delete_applied(...)
• Update docs for createWalletTransaction:
• replace client.wallet_transactions.create(...)
• to client.wallets.create_transaction(...)
• Update docs for findAllWalletTransactions:
• replace client.wallet_transactions.find_all(...)
• to client.wallets.find_all_transactions(...)

Related issue:

• Do not use client entities not related with openapi.yaml tags lago-python-client#134

Depends on:

• #134 - Do not use client entities not related with openapi.yaml tags lago-python-client#135