Update the expression of set tags in Dynamic SQL document.

[xtyuns]

The behavior of set tags was changed via #21

[harawata]

Thank you for the update, @xtyuns .

I'm sorry, my comment on #2347 was confusing.
What I suggested was to change the explanation instead of the XML code. Like this:

diff --git a/src/site/xdoc/dynamic-sql.xml b/src/site/xdoc/dynamic-sql.xml
index abc81bffcb..88f89d0086 100644
--- a/src/site/xdoc/dynamic-sql.xml
+++ b/src/site/xdoc/dynamic-sql.xml
@@ -135,7 +135,7 @@ AND title like ‘someTitle’]]></source>
   where id=#{id}
 </update>]]></source>
   <p>Here, the <em>set</em> element will dynamically prepend the SET keyword, and also eliminate any extraneous commas that might trail the value assignments after the conditions are applied.</p>
-  <p>If you’re curious about what the equivalent <em>trim</em> element would look like, here it is:</p>
+  <p>Alternatively, you can achieve the same effect by using <em>trim</em> element:</p>
   <source><![CDATA[<trim prefix="SET" suffixOverrides=",">
   ...
 </trim>]]></source>

We should not add prefixOverrides here because it's unnecessary.
And the new explanation does not say that <trim prefix="SET" suffixOverrides=","> is equivalent to <set />.

If you think it's still confusing, let's just remove this additional <trim> example.
<trim /> is already explained earlier.

diff --git a/src/site/xdoc/dynamic-sql.xml b/src/site/xdoc/dynamic-sql.xml
index abc81bffcb..676dc75336 100644
--- a/src/site/xdoc/dynamic-sql.xml
+++ b/src/site/xdoc/dynamic-sql.xml
@@ -135,11 +135,6 @@ AND title like ‘someTitle’]]></source>
   where id=#{id}
 </update>]]></source>
   <p>Here, the <em>set</em> element will dynamically prepend the SET keyword, and also eliminate any extraneous commas that might trail the value assignments after the conditions are applied.</p>
-  <p>If you’re curious about what the equivalent <em>trim</em> element would look like, here it is:</p>
-  <source><![CDATA[<trim prefix="SET" suffixOverrides=",">
-  ...
-</trim>]]></source>
-  <p>Notice that in this case we’re overriding a suffix, while we’re still appending a prefix.</p>
   </subsection>
   <subsection name="foreach">
   <p>Another common necessity for dynamic SQL is the need to iterate over a collection, often to build an IN condition. For example:</p>

[xtyuns]

You are correct, adding prefixOverrides and suffixOverrides at the same time may indeed cause confusion for users. So I prefer to modify it to your first solution: modify the equivalent to achieve the same effect

[xtyuns]

Hi @harawata, If you don't mind, I force-push the latest submission. Or I can create a new RP.

[coveralls]

Coverage remained the same at 87.224% when pulling 63de279 on xtyuns:master into 9ee6941 on mybatis:master.

[harawata]

Thank you for the update, @xtyuns !
Nice work on translations as well 👍