Repository: google/go-github (go)

Issue:
unmarshal error in billing.go - GetStorageBillingOrg function
Hello - Am trying to get the storage stats for my GitHub org from GetStorageBillingOrg function, But it throws error.
Details as follows.

_Go version used_: go1.17.2 linux/amd64
_Operating system_: Ubuntu
_Function reference_: https://github.com/google/go-github/blob/master/github/billing.go#L79

_Error_:`json: cannot unmarshal number 19.5361328125 into Go struct field StorageBilling.estimated_paid_storage_for_month of type int`

The output is on float but the struct field is of type int
https://github.com/google/go-github/blob/master/github/billing.go#L41-L45


Below is my custom function code:
```
func storage(ctx context.Context, client *github.Client, org string) {
	str, _, err := client.Billing.GetStorageBillingOrg(ctx, org)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(str)
}
```
Am able to get the response from GitHub API though
```
curl -s -u $gituser:$token -H "Accept: application/vnd.github.v3+json" https://api.github.com/orgs/$org/settings/billing/shared-storage
{
  "days_left_in_billing_cycle": 16,
  "estimated_paid_storage_for_month": 19.4375,
  "estimated_storage_for_month": 69
}
```

Pull request description:
Change StorageBilling.EstimatedPaidStorageForMonth from int to float64
fixes #2203

**Changes:**
Changed the type from int to float64 for EstimatedPaidStorageForMonth in billing.go and updated the testcases for it.

New to this repo. Please do let me know if any updates needed.

Patch:
diff --git a/github/billing.go b/github/billing.go
index fa0e034d..190140a4 100644
--- a/github/billing.go
+++ b/github/billing.go
@@ -39,9 +39,9 @@ type PackageBilling struct {
 
 // StorageBilling represents a GitHub Storage billing.
 type StorageBilling struct {
-	DaysLeftInBillingCycle       int `json:"days_left_in_billing_cycle"`
-	EstimatedPaidStorageForMonth int `json:"estimated_paid_storage_for_month"`
-	EstimatedStorageForMonth     int `json:"estimated_storage_for_month"`
+	DaysLeftInBillingCycle       int     `json:"days_left_in_billing_cycle"`
+	EstimatedPaidStorageForMonth float64 `json:"estimated_paid_storage_for_month"`
+	EstimatedStorageForMonth     int     `json:"estimated_storage_for_month"`
 }
 
 // GetActionsBillingOrg returns the summary of the free and paid GitHub Actions minutes used for an Org.


Test patch:
diff --git a/github/billing_test.go b/github/billing_test.go
index 7d1c2a1d..2693e68a 100644
--- a/github/billing_test.go
+++ b/github/billing_test.go
@@ -120,7 +120,7 @@ func TestBillingService_GetStorageBillingOrg(t *testing.T) {
 		testMethod(t, r, "GET")
 		fmt.Fprint(w, `{
 				"days_left_in_billing_cycle": 20,
-				"estimated_paid_storage_for_month": 15,
+				"estimated_paid_storage_for_month": 15.25,
 				"estimated_storage_for_month": 40
 			}`)
 	})
@@ -133,7 +133,7 @@ func TestBillingService_GetStorageBillingOrg(t *testing.T) {
 
 	want := &StorageBilling{
 		DaysLeftInBillingCycle:       20,
-		EstimatedPaidStorageForMonth: 15,
+		EstimatedPaidStorageForMonth: 15.25,
 		EstimatedStorageForMonth:     40,
 	}
 	if !cmp.Equal(hook, want) {
@@ -262,7 +262,7 @@ func TestBillingService_GetStorageBillingUser(t *testing.T) {
 		testMethod(t, r, "GET")
 		fmt.Fprint(w, `{
 				"days_left_in_billing_cycle": 20,
-				"estimated_paid_storage_for_month": 15,
+				"estimated_paid_storage_for_month": 15.25,
 				"estimated_storage_for_month": 40
 			}`)
 	})
@@ -275,7 +275,7 @@ func TestBillingService_GetStorageBillingUser(t *testing.T) {
 
 	want := &StorageBilling{
 		DaysLeftInBillingCycle:       20,
-		EstimatedPaidStorageForMonth: 15,
+		EstimatedPaidStorageForMonth: 15.25,
 		EstimatedStorageForMonth:     40,
 	}
 	if !cmp.Equal(hook, want) {