feat(deploy-config/getting-started): Clarify TIMESTAMP is int, not string

Closing: https://linear.app/optimism/issue/DEVRL-791/suggestion-l2outputoraclestartingtimestamp-needs-to-be-an-int-without

docs/op-stack/src/docs/build/getting-started.md

@@ -201,7 +201,7 @@ Once you’ve built both repositories, you’ll need head back to the Optimism M
     - Replace `"BATCHER"` with the address of the Batcher account you generated earlier.
     - Replace `"SEQUENCER"` with the address of the Sequencer account you generated earlier.
     - Replace `"BLOCKHASH"` with the blockhash you got from the `cast` command.
-    - Replace `"TIMESTAMP"` with the timestamp you got from the `cast` command. Note that although all the other fields are strings, this field is a number! Don’t include the quotation marks.
+    - Replace `TIMESTAMP` with the timestamp you got from the `cast` command. Note that although all the other fields are strings, this field is a number! Don’t include the quotation marks.
 
 ## Deploy the L1 contracts
 
@@ -578,4 +578,4 @@ To add nodes to the rollup, you need to initialize `op-node` and `op-geth`, simi
 
 ## What’s next?
 
-You can use this rollup the same way you’d use any other test blockchain. Once the superchain is available, this blockchain should be able to join the test version. Alternatively, you could [modify the blockchain in various ways](./hacks.md). **Please note that OP Stack Hacks are unofficial and are not explicitly supported by the OP Stack.** You will not be able to receive significant developer support for any modifications you make to the OP Stack.
\ No newline at end of file
+You can use this rollup the same way you’d use any other test blockchain. Once the superchain is available, this blockchain should be able to join the test version. Alternatively, you could [modify the blockchain in various ways](./hacks.md). **Please note that OP Stack Hacks are unofficial and are not explicitly supported by the OP Stack.** You will not be able to receive significant developer support for any modifications you make to the OP Stack.

packages/contracts-bedrock/deploy-config/getting-started.json

@@ -21,7 +21,7 @@
 
   "l2OutputOracleSubmissionInterval": 120,
   "l2OutputOracleStartingBlockNumber": 0,
-  "l2OutputOracleStartingTimestamp": "TIMESTAMP",
+  "l2OutputOracleStartingTimestamp": TIMESTAMP,
 
   "l2OutputOracleProposer": "PROPOSER",
   "l2OutputOracleChallenger": "ADMIN",