doc: typo Synopis

%s/Synopis/Synopsis/g

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/usage/cmd/part.rst b/doc/usage/cmd/part.rst
index 58be387..e7faecc 100644
--- a/doc/usage/cmd/part.rst
+++ b/doc/usage/cmd/part.rst
@@ -6,8 +6,8 @@
 part command
 ============
 
-Synopis
--------
+Synopsis
+--------
 
 ::