Doc: Remove 'f.i.'

Spell it out, or entirely remove it if it's not necessary.

Change-Id: Idc371427e9351d948245ce7b719e3457dfc27845
Reviewed-by: Matthew Woehlke <mwoehlke.floss@gmail.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

src/corelib/kernel/qobject.cpp

@@ -4616,7 +4616,7 @@ QDebug operator<<(QDebug dbg, const QObject *o)
     It works exactly like the Q_NAMESPACE macro. However, the external
     \c{staticMetaObject} variable that gets defined in the namespace
     is declared with the supplied \c{EXPORT_MACRO} qualifier. This is
-    useful f.i. if the object needs to be exported from a dynamic library.
+    useful if the object needs to be exported from a dynamic library.
 
     \sa Q_NAMESPACE, {Creating Shared Libraries}
 */

src/corelib/text/qregularexpression.cpp

@@ -531,7 +531,7 @@ QT_BEGIN_NAMESPACE
     optimize the execution of the matching algorithm. The JIT makes extensive
     usage of self-modifying code, which can lead debugging tools such as
     Valgrind to crash. You must enable all checks for self-modifying code if
-    you want to debug programs using QRegularExpression (f.i., see Valgrind's
+    you want to debug programs using QRegularExpression (for instance, Valgrind's
     \c{--smc-check} command line option). The downside of enabling such checks
     is that your program will run considerably slower.
 

src/gui/opengl/qopengldebug.cpp

@@ -1807,7 +1807,7 @@ QList<QOpenGLDebugMessage> QOpenGLDebugLogger::loggedMessages() const
 
     \note Message texts are encoded in UTF-8 when they get passed to OpenGL, so
     their size in bytes does not usually match the amount of UTF-16 code units,
-    as returned f.i. by QString::length(). (It does if the message contains
+    as returned, for instance, by QString::length(). (It does if the message contains
     7-bit ASCII only data, which is typical for debug messages.)
 */
 qint64 QOpenGLDebugLogger::maximumMessageLength() const