Delete schema's stakeType field from StakeData

A stake can have different stake types at the same time (T, NuInTStake
and KeepInTStake), so the StakeType's field can be misleading.

schema.graphql

@@ -1,9 +1,3 @@
-enum StakeType {
-  NU
-  KEEP
-  T
-}
-
 type Account @entity {
   # Id is the ethereum address of the account.
   id: ID!
@@ -16,7 +10,6 @@ type StakeData @entity {
   # ID is the staking provider address
   id: ID!
   owner: Account!
-  stakeType: StakeType!
   beneficiary: Bytes!
   authorizer: Bytes!
   tStake: BigInt!

src/mapping.ts

@@ -57,14 +57,13 @@ export function handleStaked(event: Staked): void {
     account.save()
   }
 
-  stakeData.stakeType = type
   stakeData.owner = account.id
   stakeData.beneficiary = event.params.beneficiary
   stakeData.authorizer = event.params.authorizer
-  stakeData.tStake = type === "T" ? amount : BigInt.zero()
-  stakeData.nuInTStake = type === "NU" ? amount : BigInt.zero()
-  stakeData.keepInTStake = type === "KEEP" ? amount : BigInt.zero()
+  stakeData.tStake = type === "T" ? stakeAmount : BigInt.zero()
+  stakeData.keepInTStake = type === "KEEP" ? stakeAmount : BigInt.zero()
   stakeData.totalStaked = stakeData.tStake
+  stakeData.nuInTStake = type === "NU" ? stakeAmount : BigInt.zero()
     .plus(stakeData.keepInTStake)
     .plus(stakeData.nuInTStake)
   stakeData.save()