fix: generate jsdocs for operations with no documentation

[kuhe]

fixes aws/aws-sdk-js-v3#5037

due to a conditional, operations with no documentation trait do not write out the default documentation additions either

(the structural type hints, example, release tags)

This PR makes the commands have at least a default documentation even when none exists in the model.

• JSv3 codegen testing

[kuhe]

Example for ExportApi operation in apigatewayv2 in the AWS SDK for JSv3

/**
 * @public
 *
 * @example
 * Use a bare-bones client and the command you need to make an API call.
 * ```javascript
 * import { ApiGatewayV2Client, ExportApiCommand } from "@aws-sdk/client-apigatewayv2"; // ES Modules import
 * // const { ApiGatewayV2Client, ExportApiCommand } = require("@aws-sdk/client-apigatewayv2"); // CommonJS import
 * const client = new ApiGatewayV2Client(config);
 * const input = { // ExportApiRequest
 *   ApiId: "STRING_VALUE", // required
 *   ExportVersion: "STRING_VALUE",
 *   IncludeExtensions: true || false,
 *   OutputType: "STRING_VALUE", // required
 *   Specification: "STRING_VALUE", // required
 *   StageName: "STRING_VALUE",
 * };
 * const command = new ExportApiCommand(input);
 * const response = await client.send(command);
 * // { // ExportApiResponse
 * //   body: "BLOB_VALUE",
 * // };
 *
 * ```
 *
 * @param ExportApiCommandInput - {@link ExportApiCommandInput}
 * @returns {@link ExportApiCommandOutput}
 * @see {@link ExportApiCommandInput} for command's `input` shape.
 * @see {@link ExportApiCommandOutput} for command's `response` shape.
 * @see {@link ApiGatewayV2ClientResolvedConfig | config} for ApiGatewayV2Client's `config` shape.
 *
 * @throws {@link BadRequestException} (client fault)
 *  <p>The request is not valid, for example, the input is incomplete or incorrect. See the accompanying error message for details.</p>
 *
 * @throws {@link NotFoundException} (client fault)
 *  <p>The resource specified in the request was not found. See the message field for more information.</p>
 *
 * @throws {@link TooManyRequestsException} (client fault)
 *  <p>A limit has been exceeded. See the accompanying error message for details.</p>
 *
 * @throws {@link ApiGatewayV2ServiceException}
 * <p>Base exception class for all service exceptions from ApiGatewayV2 service.</p>
 *
 */

(compared to empty docs currently)