Clarify comment in RFC Template (#3462)

Looking at the RFC template file, I thought that the recommendation to
leave the software design section empty referred to everything below the
comment, rather than just that section. This PR updates the comment.

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under the terms of the Apache 2.0 and MIT licenses.

Author: carolynzech

rfc/src/template.md

@@ -43,6 +43,8 @@ No further explanation is needed.
 
 ## Software Design
 
+**We recommend that you leave the Software Design section empty for the first version of your RFC**.
+
 This is the beginning of the technical portion of the RFC.
 From now on, your main audience is Kani developers, so it's OK to assume readers know Kani architecture.
 
@@ -53,8 +55,6 @@ Please provide a high level description your design.
 - Any changes to how these components communicate?
 - What corner cases do you anticipate?
 
-**We recommend you to leave this empty for the first version of your RFC**.
-
 ## Rationale and alternatives
 
 This is the section where you discuss the decisions you made.