Fix governance:build-proposal bigNumber bug (#8028)

Looks like this was related to ethers-io/ethers.js#228, but we just need to force the bignumber string to not be in scientific notation when transforming the value, and then this works as expected. Note that the outputted value in the outputted transaction will **not** be in scientific notation.

Closes #7466

packages/sdk/governance/src/proposals.ts

@@ -370,8 +370,9 @@ export class InteractiveProposalBuilder {
 
         // @ts-ignore
         const answer: string = inputAnswer[functionInput.name]
+        // transformedValue may not be in scientific notation
         const transformedValue =
-          functionInput.type === 'uint256' ? new BigNumber(answer).toString() : answer
+          functionInput.type === 'uint256' ? new BigNumber(answer).toString(10) : answer
         args.push(transformedValue)
       }