minor #11576 Change wording about time for downstream projects (BackEndTea)

This PR was submitted for the master branch but it was merged into the 3.4 branch instead (closes #11576).

Discussion
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Change wording about time for downstream projects

I felt the wording here was a bit off. The 'seems like' made it feel like this is something that is still being considered.

Commits
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1c4d8fc Change wording about time for downstream projects

Author: javiereguiluz

contributing/code/security.rst

@@ -78,7 +78,7 @@ projects. The process works as follows:
    date for a joint release (there is no guarantee that all releases will
    be at the same time but we will try hard to make them at about the same
    time). When the issue is not known to be exploited in the wild, a period
-   of two weeks seems like a reasonable amount of time.
+   of two weeks is considered a reasonable amount of time.
 
 The list of downstream projects participating in this process is kept as small
 as possible in order to better manage the flow of confidential information