QProcess: remove no-op std::move()

You cannot move into QString::arg()¹, so don't confuse readers by
attempting to try.

¹ There's also never going to be a version of arg() where you _can_
  move into, because string interpolation is inherently a read-only
  operation that doesn't require ownership. The only conceivable
  situation is pinning of rvalues for the duration of the operation,
  as done in QStringBuilder and QStringTokenizer, but that would be
  an implicit move by the language, not a std::move().

Amends 030c93a.

Task-number: QTBUG-144875
Change-Id: Idc4429250f23b964e89c3941561783d9e704b71c
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit bbfe8f5)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 43d773a)

Author: marcmutz

src/corelib/io/qprocess_unix.cpp

@@ -193,7 +193,7 @@ static constexpr int FakeErrnoForThrow = std::numeric_limits<int>::max();
 static QString errorMessageForSyscall(QUtf8StringView fnName, int errnoCode = -1)
 {
     QString msg = qt_error_string(errnoCode);
-    return QProcess::tr("Child process set up failed: %1: %2").arg(fnName, std::move(msg));
+    return QProcess::tr("Child process set up failed: %1: %2").arg(fnName, msg);
 }
 
 static QString startFailureErrorMessage(ChildError &err, [[maybe_unused]] ssize_t bytesRead)