Remove TODOs in samples to "release stuff".

Now WebGPU objects can be destroyed in any order without the risk of
causing segfaults.

Bug: None
Change-Id: I00aecf49aa65308c13ab0accc69152fa1361d714
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/84768
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Loko Kung <lokokung@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

samples/dawn/Animometer.cpp

@@ -189,6 +189,4 @@ int main(int argc, const char* argv[]) {
         frame();
         utils::USleep(16000);
     }
-
-    // TODO release stuff
 }

samples/dawn/CHelloTriangle.cpp

@@ -152,6 +152,4 @@ int main(int argc, const char* argv[]) {
         frame();
         utils::USleep(16000);
     }
-
-    // TODO release stuff
 }

samples/dawn/ComputeBoids.cpp

@@ -327,6 +327,4 @@ int main(int argc, const char* argv[]) {
         frame();
         utils::USleep(16000);
     }
-
-    // TODO release stuff
 }

samples/dawn/CppHelloTriangle.cpp

@@ -181,6 +181,4 @@ int main(int argc, const char* argv[]) {
         frame();
         utils::USleep(16000);
     }
-
-    // TODO release stuff
 }