fix: clarify InnoDB is recommended but not the default engine

Cacti installs Boost tables as MEMORY by default; calling InnoDB 'the
default' was misleading. Rephrase to 'recommended' and note conversion
steps exist below.

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

Author: somethingwithproof

Boost.md

@@ -45,7 +45,8 @@ increase overall performance, and to reduce writing data to disk. With
 improvements in InnoDB performance over the years combined with Flash storage,
 the need for MySQL Memory Tables has diminished. The sections below document
 MEMORY table sizing for sites that have an explicit reason to use it, but InnoDB
-is the default and recommended engine.
+is the recommended engine. Cacti installs MEMORY tables by default; see below
+for the conversion steps.
 
 If you do wish to use Memory you have to pay close attention to the amount of
 data that will be cached in your design. You should periodically check that you