Ecotone specs: clarify post-Ecotone handling of overhead/scalar values (#8997)

* clarify overhead/scalar values are irrelevant after Ecotone upgrade block

* specs: clarify ecotone L1 attributes call

---------
Co-authored-by: protolambda <proto@protolambda.com>

specs/deposits.md

@@ -338,8 +338,8 @@ The predeploy stores the following values:
   - `baseFeeScalar` (`uint32`): system configurable to scale the `basefee` in the Ecotone l1 cost computation
   - `blobBasefeeScalar` (`uint32`): system configurable to scale the `blobBaseFee` in the Ecotone l1 cost computation
 
-Following the Ecotone upgrade, `overhead` and `scalar` are frozen at the values they had on the
-block immediately prior to the fork.
+The `overhead` and `scalar` values can continue to be accessed after the Ecotone activation block,
+but no longer have any effect on system operation.
 
 The contract implements an authorization scheme, such that it only accepts state-changing calls from
 the [depositor account][depositor-account].
@@ -371,11 +371,16 @@ begins to store additional data:
 - `blobBaseFeeScalar` (`uint32`): The scalar value applied to the L1 blob base fee portion of the L1 cost.
 - `baseFeeScalar` (`uint32`): The scalar value applied to the L1 base fee portion of the L1 cost.
 
-Additionally, the `setL1BlockValues` function is deprecated and MUST never be called when the L2 block number
-is greater than the Ecotone activation block number. `setL1BlockValues` MUST be called on the Ecotone hardfork
-activation block, except if activated at genesis.
-The `setL1BlockValuesEcotone` MUST be called when the L2 block number is greater than the Ecotone hardfork
-activation block.
+The function called by the L1 attributes transaction depends on the network upgrade:
+
+- Before the Ecotone activation:
+  - `setL1BlockValues` is called, following the pre-Ecotone L1 attributes rules.
+- At the Ecotone activation block:
+  - `setL1BlockValues` function MUST be called, except if activated at genesis.
+    The contract is upgraded later in this block, to support `setL1BlockValuesEcotone`.
+- After the Ecotone activation:
+  - `setL1BlockValues` function is deprecated and MUST never be called.
+  - `setL1BlockValuesEcotone` MUST be called with the new Ecotone attributes.
 
 `setL1BlockValuesEcotone` uses a tightly packed encoding for its parameters, which is described in
 [L1 Attributes Deposited Transaction Calldata](#l1-attributes-deposited-transaction-calldata).