Remove optional revert error return types from web3-eth TS definitions

[cgewecke]

Description

PR removes error return types which cause tsc compilation errors when used in a statement that declares a type for the LHS of some web3-eth methods. The error isn't really a return value, it's the type of the error object passed to the catch clause.

For example:

const a: TransactionReceipt = await sendTransaction(...)

...currently throws

error TS2322: Type 'TransactionRevertInstructionError | TransactionReceipt' is not assignable 
to type 'TransactionReceipt'. Type 'TransactionRevertInstructionError' is missing 
the following properties from type 'TransactionReceipt': status, transactionHash, 
transactionIndex, blockHash, and 7 more.

(Looked around at a few TS projects to see how (or if) defining custom error types for Promise rejections is done but don't see a lot of examples. )

Fixes #3496

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run dtslint with success and extended the tests and types if necessary.
• I have updated the CHANGELOG.md file in the root folder.

[ryanio]

(Looked around at a few TS projects to see how (or if) defining custom error types for Promise rejections is done but don't see a lot of examples. )

It looks like this continues to be under discussion in microsoft/TypeScript#20024.

Otherwise, PR LGTM!