tutorials: fix typos

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1669>

subprojects/gst-docs/markdown/tutorials/basic/media-information-gathering.md

@@ -256,7 +256,7 @@ int main (int argc, char **argv) {
     uri = argv[1];
   }
 
-  /* Initialize cumstom data structure */
+  /* Initialize custom data structure */
   memset (&data, 0, sizeof (data));
 
   /* Initialize GStreamer */

subprojects/gst-docs/markdown/tutorials/playback/short-cutting-the-pipeline.md

@@ -148,7 +148,7 @@ int main(int argc, char *argv[]) {
   CustomData data;
   GstBus *bus;
 
-  /* Initialize cumstom data structure */
+  /* Initialize custom data structure */
   memset (&data, 0, sizeof (data));
   data.b = 1; /* For waveform generation */
   data.d = 1;