DOC: ssl: fix typo about ocsp files

one of the last I saw in this section while working on github issue #872

might be backported in all still supported versions

Signed-off-by: William Dauchy <w.dauchy@criteo.com>
diff --git a/doc/configuration.txt b/doc/configuration.txt
index f6eacfb..ef9ca4b 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -1423,7 +1423,7 @@
   On the CLI, bundles are seen as separate files, and the bundle extension is
   required to commit them.
 
-  OSCP files (.ocsp), issuer files (.issuer), Certificate Transparency (.sctl)
+  OCSP files (.ocsp), issuer files (.issuer), Certificate Transparency (.sctl)
   as well as private keys (.key) are supported with multi-cert bundling.
 
   "sctl": Try to load "<basename>.sctl" for each crt keyword.