fix(transcoder): update the API

#### transcoder:v1beta1

The following keys were changed:
- schemas.VideoStream.properties.frameRate.description

discovery/transcoder-v1beta1.json

@@ -355,7 +355,7 @@
       }
     }
   },
-  "revision": "20210323",
+  "revision": "20210405",
   "rootUrl": "https://transcoder.googleapis.com/",
   "schemas": {
     "AdBreak": {
@@ -1478,7 +1478,7 @@
           "type": "string"
         },
         "frameRate": {
-          "description": "Required. The target video frame rate in frames per second (FPS). Must be less than or equal to 120. Will default to the input frame rate if larger than the input frame rate. The API will generate an output FPS that is divisible by the input FPS, and smaller or equal to the target FPS. The following table shows the computed video FPS given the target FPS (in parenthesis) and input FPS (in the first column): ``` | | (30) | (60) | (25) | (50) | |--------|--------|--------|------|------| | 240 | Fail | Fail | Fail | Fail | | 120 | 30 | 60 | 20 | 30 | | 100 | 25 | 50 | 20 | 30 | | 50 | 25 | 50 | 20 | 30 | | 60 | 30 | 60 | 20 | 30 | | 59.94 | 29.97 | 59.94 | 20 | 30 | | 48 | 24 | 48 | 20 | 30 | | 30 | 30 | 30 | 20 | 30 | | 25 | 25 | 25 | 20 | 30 | | 24 | 24 | 24 | 20 | 30 | | 23.976 | 23.976 | 23.976 | 20 | 30 | | 15 | 15 | 15 | 20 | 30 | | 12 | 12 | 12 | 20 | 30 | | 10 | 10 | 10 | 20 | 30 | ```",
+          "description": "Required. The target video frame rate in frames per second (FPS). Must be less than or equal to 120. Will default to the input frame rate if larger than the input frame rate. The API will generate an output FPS that is divisible by the input FPS, and smaller or equal to the target FPS. See [Calculate frame rate](https://cloud.google.com/transcoder/docs/concepts/frame-rate) for more information.",
           "format": "double",
           "type": "number"
         },

src/apis/transcoder/v1beta1.ts

@@ -994,7 +994,7 @@ export namespace transcoder_v1beta1 {
      */
     entropyCoder?: string | null;
     /**
-     * Required. The target video frame rate in frames per second (FPS). Must be less than or equal to 120. Will default to the input frame rate if larger than the input frame rate. The API will generate an output FPS that is divisible by the input FPS, and smaller or equal to the target FPS. The following table shows the computed video FPS given the target FPS (in parenthesis) and input FPS (in the first column): ``` | | (30) | (60) | (25) | (50) | |--------|--------|--------|------|------| | 240 | Fail | Fail | Fail | Fail | | 120 | 30 | 60 | 20 | 30 | | 100 | 25 | 50 | 20 | 30 | | 50 | 25 | 50 | 20 | 30 | | 60 | 30 | 60 | 20 | 30 | | 59.94 | 29.97 | 59.94 | 20 | 30 | | 48 | 24 | 48 | 20 | 30 | | 30 | 30 | 30 | 20 | 30 | | 25 | 25 | 25 | 20 | 30 | | 24 | 24 | 24 | 20 | 30 | | 23.976 | 23.976 | 23.976 | 20 | 30 | | 15 | 15 | 15 | 20 | 30 | | 12 | 12 | 12 | 20 | 30 | | 10 | 10 | 10 | 20 | 30 | ```
+     * Required. The target video frame rate in frames per second (FPS). Must be less than or equal to 120. Will default to the input frame rate if larger than the input frame rate. The API will generate an output FPS that is divisible by the input FPS, and smaller or equal to the target FPS. See [Calculate frame rate](https://cloud.google.com/transcoder/docs/concepts/frame-rate) for more information.
      */
     frameRate?: number | null;
     /**