Temp remove api ref content for indexer (MystenLabs#10779)

## Description 

Temporarily removes indexer-specific api methods.
 * getEpochs
 * getCurrentEpoch
 * getNetworkMetrics
 * getMoveCallMetrics

## Test Plan 

Local

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### Type of Change (Check all that apply)

- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes