[JIT] Fix archive file extension in examples and docs (#50649)

Summary:
Pull Request resolved: #50649

**Summary**
Tutorials, documentation and comments are not consistent with the file
extension they use for JIT archives. This commit modifies certain
instances of `*.pth` in `torch.jit.save` calls with `*.pt`.

**Test Plan**
Continuous integration.

**Fixes**
This commit fixes #49660.

Test Plan: Imported from OSS

Reviewed By: ZolotukhinM

Differential Revision: D25961628

Pulled By: SplitInfinity

fbshipit-source-id: a40c97954adc7c255569fcec1f389aa78f026d47

docs/source/jit.rst

@@ -548,17 +548,17 @@ best practices?
       cpu_model = gpu_model.cpu()
       sample_input_cpu = sample_input_gpu.cpu()
       traced_cpu = torch.jit.trace(cpu_model, sample_input_cpu)
-      torch.jit.save(traced_cpu, "cpu.pth")
+      torch.jit.save(traced_cpu, "cpu.pt")
 
       traced_gpu = torch.jit.trace(gpu_model, sample_input_gpu)
-      torch.jit.save(traced_gpu, "gpu.pth")
+      torch.jit.save(traced_gpu, "gpu.pt")
 
       # ... later, when using the model:
 
       if use_gpu:
-        model = torch.jit.load("gpu.pth")
+        model = torch.jit.load("gpu.pt")
       else:
-        model = torch.jit.load("cpu.pth")
+        model = torch.jit.load("cpu.pt")
 
       model(input)
 

test/cpp/jit/test_graph_executor.cpp

@@ -44,7 +44,7 @@ TEST(GraphExecutorTest, runAsync_executor) {
         r2 = torch.jit.fork(torch.mm, torch.rand(100,100),torch.rand(100,100))
         return r1.wait() + r2.wait()
   demo = DemoModule()
-  torch.jit.save(torch.jit.script(demo), 'test_interpreter_async.pth')
+  torch.jit.save(torch.jit.script(demo), 'test_interpreter_async.pt')
   */
   std::string filePath(__FILE__);
   auto testModelFile = filePath.substr(0, filePath.find_last_of("/\\") + 1);

test/cpp/jit/test_interpreter.cpp

@@ -155,7 +155,7 @@ TEST(InterpreterTest, runAsyncBasicTest) {
         r2 = torch.jit.fork(torch.mm, torch.rand(100,100),torch.rand(100,100))
         return r1.wait() + r2.wait()
   demo = DemoModule()
-  torch.jit.save(torch.jit.script(demo), 'test_interpreter_async.pth')
+  torch.jit.save(torch.jit.script(demo), 'test_interpreter_async.pt')
   */
   std::string filePath(__FILE__);
   auto testModelFile = filePath.substr(0, filePath.find_last_of("/\\") + 1);