Fixed #30573 -- Rephrased documentation to avoid words that minimise the involved difficulty.

This patch does not remove all occurrences of the words in question.
Rather, I went through all of the occurrences of the words listed
below, and judged if they a) suggested the reader had some kind of
knowledge/experience, and b) if they added anything of value (including
tone of voice, etc). I left most of the words alone. I looked at the
following words:

- simply/simple
- easy/easier/easiest
- obvious
- just
- merely
- straightforward
- ridiculous

Thanks to Carlton Gibson for guidance on how to approach this issue, and
to Tim Bell for providing the idea. But the enormous lion's share of
thanks go to Adam Johnson for his patient and helpful review.

docs/topics/performance.txt

@@ -86,7 +86,7 @@ Get things right from the start
 -------------------------------
 
 Some work in optimization involves tackling performance shortcomings, but some
-of the work can simply be built in to what you'd do anyway, as part of the good
+of the work can be built in to what you'd do anyway, as part of the good
 practices you should adopt even before you start thinking about improving
 performance.
 
@@ -353,7 +353,7 @@ Newer is often - but not always - better
 It's fairly rare for a new release of well-maintained software to be less
 efficient, but the maintainers can't anticipate every possible use-case - so
 while being aware that newer versions are likely to perform better, don't
-simply assume that they always will.
+assume that they always will.
 
 This is true of Django itself. Successive releases have offered a number of
 improvements across the system, but you should still check the real-world