var-declaration linting errors from revive linter

[atc0005]

Surfaced by #266:

internal/textutils/inspect_test.go:23:20: var-declaration: should drop = nil from declaration of var want; it is the zero value (revive)
		var want error = nil
		                 ^
internal/textutils/inspect_test.go:42:20): var-declaration: should drop = nil from declaration of var want; it is the zero value (revive)
		var want error = nil
		                 ^
internal/config/config.go:23:13: var-declaration: should omit type string from declaration of var version; it will be inferred from the right-hand side (revive)
var version string = "x.y.z"
            ^