Make cmd/pscale `go install`-able

从 cmd/pscale 和 go.mod 中唯一的 replace 指令开始，然后运行 go install github.com/planetscale/cli/cmd/pscale@latest 以重现报告的失败。追踪被替换的依赖项，并验证该命令能够成功安装，且没有 replace 指令影响模块安装。

It would be great if some of us Go users can install/update the pscale library by just doing go install github.com/planetscale/cli/cmd/pscale@latest

However, due to the 1 replace directive, go install refuses to install binaries that have a replace directive in them:

$ go install github.com/planetscale/cli/cmd/pscale@latest
go: downloading github.com/planetscale/cli v0.177.0
go: github.com/planetscale/cli/cmd/pscale@latest (in github.com/planetscale/cli@v0.177.0):
	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.

Looking at the go.mod file, there's only one replace clause, which seems like a hopefully small lift (by either changing the import path of the fork), or resolving whatever is being replaced upstream would unable this helpful feature.

Thanks!