QLockFile: remove unneeded tryLock_impl middle-man

It's perfectly ok to de-inline a function, even an exported one, so
remove the tryLock_impl() middle-man and pull the Qt 7 pre-programming
into the here and now.

Amends 5cea5fc80b9e1b19d620ec6be1acd5cdbd220971.

Change-Id: I7e9626a91d8ebd64e02c3784c74621950da669fb
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>
(cherry picked from commit 508629522d8c6580161a2fd9bfd2fe26f6c4c034)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/io/qlockfile.cpp

@@ -257,7 +257,7 @@ bool QLockFile::tryLock(int timeout)
     return tryLock(std::chrono::milliseconds{ timeout });
 }
 
-/*! \fn bool QLockFile::tryLock(std::chrono::milliseconds timeout)
+/*!
     \overload
     \since 6.2
 
@@ -275,11 +275,7 @@ bool QLockFile::tryLock(int timeout)
 
     \sa lock(), unlock()
 */
-#if QT_VERSION >= QT_VERSION_CHECK(7, 0, 0)
 bool QLockFile::tryLock(std::chrono::milliseconds timeout)
-#else
-bool QLockFile::tryLock_impl(std::chrono::milliseconds timeout)
-#endif
 {
     using namespace std::chrono_literals;
     using Msec = std::chrono::milliseconds;

src/corelib/io/qlockfile.h

@@ -28,14 +28,7 @@ public:
     void setStaleLockTime(int);
     int staleLockTime() const;
 
-#if QT_VERSION >= QT_VERSION_CHECK(7, 0, 0)
     bool tryLock(std::chrono::milliseconds timeout = std::chrono::milliseconds::zero());
-#else
-    bool tryLock(std::chrono::milliseconds timeout = std::chrono::milliseconds::zero())
-    {
-        return tryLock_impl(timeout);
-    }
-#endif
 
     void setStaleLockTime(std::chrono::milliseconds value);
     std::chrono::milliseconds staleLockTimeAsDuration() const;
@@ -58,10 +51,6 @@ protected:
 private:
     Q_DECLARE_PRIVATE(QLockFile)
     Q_DISABLE_COPY(QLockFile)
-
-#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
-    bool tryLock_impl(std::chrono::milliseconds timeout);
-#endif
 };
 
 QT_END_NAMESPACE