fix(cos): [122768427] tencentcloud_cos_buckets Fix the issue of query errors (#3287)

* add

* add

Author: SevenEarth

Diff for: .changelog/3287.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+datasource/tencentcloud_cos_buckets: Fix the issue of query errors
+```

Diff for: tencentcloud/services/cos/data_source_tc_cos_buckets.go

@@ -261,11 +261,8 @@ func DataSourceTencentCloudCosBuckets() *schema.Resource {
 									//	Description: "",
 									//},
 									"follow_http_headers": {
-										Type:     schema.TypeSet,
-										Optional: true,
-										Set: func(i interface{}) int {
-											return helper.HashString(i.(string))
-										},
+										Type:        schema.TypeList,
+										Optional:    true,
 										Description: "Specifies the pass through headers when accessing the origin server.",
 										Elem:        &schema.Schema{Type: schema.TypeString},
 									},

Diff for: tencentcloud/services/cos/service_tencentcloud_cos.go

@@ -1339,7 +1339,7 @@ func (me *CosService) GetBucketPullOrigin(ctx context.Context, bucket string) (r
 					for _, header := range rule.OriginParameter.HttpHeader.FollowHttpHeaders {
 						headers.Add(header.Key)
 					}
-					item["follow_http_headers"] = headers
+					item["follow_http_headers"] = headers.List()
 				}
 
 			}