doc: remove "is recommended" from crypto legacy API text
The text for the legacy API sends mixed signals. It's legacy, but still supported, so not deprecated, but not recommended. Let's begin to clarify this by removing "not recommended". If we want to not-recommend it, let's doc-deprecate it properly, or at least include an explanation as to why it's not recommended.
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines