docs: document 200 OK response for upload file API when file exists (#21071)

Co-authored-by: blink-so[bot] <211532188+blink-so[bot]@users.noreply.github.com>

coderd/apidoc/docs.go

@@ -1290,8 +1290,14 @@ const docTemplate = `{
                     }
                 ],
                 "responses": {
+                    "200": {
+                        "description": "Returns existing file if duplicate",
+                        "schema": {
+                            "$ref": "#/definitions/codersdk.UploadResponse"
+                        }
+                    },
                     "201": {
-                        "description": "Created",
+                        "description": "Returns newly created file",
                         "schema": {
                             "$ref": "#/definitions/codersdk.UploadResponse"
                         }

coderd/apidoc/swagger.json

@@ -1116,8 +1116,14 @@
 					}
 				],
 				"responses": {
+					"200": {
+						"description": "Returns existing file if duplicate",
+						"schema": {
+							"$ref": "#/definitions/codersdk.UploadResponse"
+						}
+					},
 					"201": {
-						"description": "Created",
+						"description": "Returns newly created file",
 						"schema": {
 							"$ref": "#/definitions/codersdk.UploadResponse"
 						}