Deshim //folly/experimental:singleton_relaxed_counter in fbcode

Summary:
The following rules were deshimmed:
```
//folly/experimental:singleton_relaxed_counter -> //folly/concurrency:singleton_relaxed_counter
```

The following headers were deshimmed:
```
folly/experimental/SingletonRelaxedCounter.h -> folly/concurrency/SingletonRelaxedCounter.h
```

This is a codemod. It was automatically generated and will be landed once it is approved and tests are passing in sandcastle.
You have been added as a reviewer by Sentinel or Butterfly.

Autodiff project: desrc
Autodiff partition: fbcode
Autodiff bookmark: ad.desrc.fbcode

Reviewed By: Orvid

Differential Revision: D60478350

fbshipit-source-id: 5fac46815e397ba609ffedce556de621e2444533

folly/concurrency/test/BUCK

@@ -184,7 +184,7 @@ cpp_binary(
     ],
     deps = [
         "//folly:benchmark",
-        "//folly/experimental:singleton_relaxed_counter",
+        "//folly/concurrency:singleton_relaxed_counter",
         "//folly/init:init",
         "//folly/lang:keep",
         "//folly/portability:gflags",
@@ -201,7 +201,7 @@ cpp_unittest(
     ],
     deps = [
         "//folly:thread_local",
-        "//folly/experimental:singleton_relaxed_counter",
+        "//folly/concurrency:singleton_relaxed_counter",
         "//folly/portability:gtest",
     ],
     external_deps = [

folly/concurrency/test/SingletonRelaxedCounterBench.cpp

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include <folly/experimental/SingletonRelaxedCounter.h>
+#include <folly/concurrency/SingletonRelaxedCounter.h>
 
 #include <cstddef>
 #include <thread>

folly/concurrency/test/SingletonRelaxedCounterTest.cpp

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include <folly/experimental/SingletonRelaxedCounter.h>
+#include <folly/concurrency/SingletonRelaxedCounter.h>
 
 #include <cstddef>
 #include <thread>