update wtxmgr require for a replace-free release

[chappjc]

Resolves #780

This is essentially what I would propose to resolve issue #780.
Except, there would ideally be a wtxmgr/v1.4.0 tag instead of a require to for an untagged revision.

The btcd required update is not strictly necessary, and should actually probably be skipped.
On the other hand, the neutrino update to v0.13.0 is more important as there is a critical bug fixed in that release.

[chappjc]

Closing since other module tasks related to the new btcd/btcutil submodule that will obsolete these changes.

I would just respectfully request that either (a) the next tagged release could be cut without the replaces so that Go consumers (not just the btcwallet app when built from the root of the repository) can require the btcwallet module without additional replace or require directives to get compatible wtxmgr etc. submodules, or (b) ensure that any replaces aren't needed to build.

Plus it's nice for install instructions if you could do go install to get the btcwallet app without manually checking out the workspace and building from the main module folder (repo root).

$  go install -v github.com/btcsuite/btcwallet@v0.13.0
go install: github.com/btcsuite/btcwallet@v0.13.0 (in github.com/btcsuite/btcwallet@v0.13.0):
	The go.mod file for the module providing named packages contains one or
	more replace directives. It must not contain directives that would cause
	it to be interpreted differently than if it were the main module.

Also would be good to bump the versions in version.go.

I appreciate all the effort to maintain btcwallet in the age of cumbersome Go modules. Thanks!