[Documentation]: depinject examples are wrong

[tbruyelle]

Summary

In depinject/README.md, all code examples use function literals as providers, but this is not authorized any more.

cosmos-sdk/depinject/README.md

Lines 33 to 65 in 36a9330

	By leveraging `depinject` and its Configuration API, you can efficiently handle dependencies in your blockchain application, ensuring a clean, modular, and well-organised codebase.
	Example:
	```go
	package main
	import (
	"fmt"
	"cosmossdk.io/depinject"
	)
	type AnotherInt int
	func main() {
	var (
	x int
	y AnotherInt
	)
	fmt.Printf("Before (%v, %v)\n", x, y)
	depinject.Inject(
	depinject.Provide(
	func() int { return 1 },
	func() AnotherInt { return AnotherInt(2) },
	),
	&x,
	&y,
	)
	fmt.Printf("After (%v, %v)\n", x, y)
	}
	```

If you execute the code in example, depinject.Inject will return an error Failed registering providers because of: function must be exported: main.main.func1.

I don't know the reason of why this isn't authorized any more, but now this example should actually looks like that :

func GetInt() int               { return 1 }
func GetAnotherInt() AnotherInt { return 2 }

func main() {
	var (
		x int
		y AnotherInt
	)

	fmt.Printf("Before (%v, %v)\n", x, y)
	depinject.Inject(
		depinject.Provide(
			GetInt,
			GetAnotherInt,
		),
		&x,
		&y,
	)
	fmt.Printf("After (%v, %v)\n", x, y)
}

[julienrbrt]

The reason was to eventually support codegen in depinject: #12556.
That's a good catch, thanks! Do you want to submit a PR?

[tbruyelle]

OK thanks for the rational.

Do you want to submit a PR?

Sure I can do that.