DOC: name set-gpt0 mismatch with the expected keyword

replace set-gpt0 by sc-set-gpt0

must be backported in 1.6
diff --git a/doc/configuration.txt b/doc/configuration.txt
index d882b05..6b80158 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -8722,7 +8722,7 @@
     - capture : the specified sample expression is captured
     - { track-sc0 | track-sc1 | track-sc2 } <key> [table <table>]
     - sc-inc-gpc0(<sc-id>)
-    - set-gpt0(<sc-id>) <int>
+    - sc-set-gpt0(<sc-id>) <int>
     - set-var(<var-name>) <expr>
     - silent-drop