[llvm] [llvm-exegesis] Remove unused Counter::read method (PR #76651)

[Clement Courbet via llvm-commits]

================
@@ -356,7 +356,11 @@ class SubProcessFunctionExecutorImpl
       if (ChildExitCode == 0) {
         // The child exited succesfully, read counter values and return
         // success
-        CounterValues[0] = Counter->read();
+        auto CounterValueOrErr = Counter->readOrError();
+        if (!CounterValueOrErr)
+          return CounterValueOrErr.takeError();
+        CounterValues.swap(*CounterValueOrErr);
----------------
legrosbuffle wrote:

Any reason not to write `CounterValues = *std::move(CounterValueOrErr);` ?

https://github.com/llvm/llvm-project/pull/76651