sui-indexer: fix CLI clap error (#21158)

## Description 

an issue reported by community 

#21037 (comment)

introduced in 
#20783

the error was 
```
Argument `gc_checkpoint_files`'s selected action SetTrue contradicts `takes_value`
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

## Test plan 

```
DB_POOL_SIZE=10 cargo run --bin sui-indexer -- --db-url "postgres://postgres:postgrespw@localhost:5432/gegao" indexer --remote-store-url https://checkpoints.mainnet.sui.io 
DB_POOL_SIZE=10 cargo run --bin sui-indexer -- --db-url "postgres://postgres:postgrespw@localhost:5432/gegao" indexer --remote-store-url https://checkpoints.mainnet.sui.io --gc-checkpoint-files
DB_POOL_SIZE=10 cargo run --bin sui-indexer -- --db-url "postgres://postgres:postgrespw@localhost:5432/gegao" indexer --remote-store-url https://checkpoints.mainnet.sui.io --gc-checkpoint-files=true
DB_POOL_SIZE=10 cargo run --bin sui-indexer -- --db-url "postgres://postgres:postgrespw@localhost:5432/gegao" indexer --remote-store-url https://checkpoints.mainnet.sui.io --gc-checkpoint-files=false
DB_POOL_SIZE=10 cargo run --bin sui-indexer -- --db-url "postgres://postgres:postgrespw@localhost:5432/gegao" indexer --remote-store-url https://checkpoints.mainnet.sui.io --gc-checkpoint-files true
DB_POOL_SIZE=10 cargo run --bin sui-indexer -- --db-url "postgres://postgres:postgrespw@localhost:5432/gegao" indexer --remote-store-url https://checkpoints.mainnet.sui.io --gc-checkpoint-files false
```


---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

For each box you select, include information after the relevant heading
that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] gRPC:
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:

crates/sui-indexer/src/config.rs

@@ -146,6 +146,7 @@ pub struct IngestionConfig {
         long,
         default_value_t = true,
         default_missing_value = "true",
+        action = clap::ArgAction::Set,
         num_args = 0..=1,
         require_equals = false,
     )]