docs: fix migrations directory (#9746)

Co-authored-by: ryanchrypto <[email protected]>

docs/architecture/adr-041-in-place-store-migrations.md

@@ -66,12 +66,12 @@ type Migrator struct {
 }
 ```
 
-Since migration functions manipulate legacy code, they should live inside the `legacy/` folder of each module, and be called by the Migrator's methods. We propose the format `Migrate{M}to{N}` for method names.
+Migration functions should live inside the `migrations/` folder of each module, and be called by the Migrator's methods. We propose the format `Migrate{M}to{N}` for method names.
 
 ```go
 // Migrate1to2 migrates from version 1 to 2.
 func (m Migrator) Migrate1to2(ctx sdk.Context) error {
-	return v043bank.MigrateStore(ctx, m.keeper.storeKey) // v043bank is package `x/bank/legacy/v043`.
+	return v043bank.MigrateStore(ctx, m.keeper.storeKey) // v043bank is package `x/bank/migrations/v043`.
 }
 ```
 

docs/building-modules/upgrade.md

@@ -45,12 +45,12 @@ Since these migrations are functions that need access to a Keeper's store, use a
 
 ## Writing Migration Scripts
 
-To define the functionality that takes place during an upgrade, write a migration script. Since migration scripts manipulate legacy code, place these functions in a `legacy/` directory. For example, to write migration scripts for the bank module, place the functions in `x/bank/legacy/`. Use the recommended naming convention for these functions. For example, `v043bank` is the script that migrates this legacy package `x/bank/legacy/v043`:
+To define the functionality that takes place during an upgrade, write a migration script and place the functions in a `migrations/` directory. For example, to write migration scripts for the bank module, place the functions in `x/bank/migrations/`. Use the recommended naming convention for these functions. For example, `v043bank` is the script that migrates the package `x/bank/migrations/v043`:
 
 ```golang
 // Migrating bank module from version 1 to 2
 func (m Migrator) Migrate1to2(ctx sdk.Context) error {
-	return v043bank.MigrateStore(ctx, m.keeper.storeKey) // v043bank is package `x/bank/legacy/v043`.
+	return v043bank.MigrateStore(ctx, m.keeper.storeKey) // v043bank is package `x/bank/migrations/v043`.
 }
 ```