Fixed typo

Signed-off-by: Andriy Redko <[email protected]>

Author: reta

po/uk.po

@@ -1803,7 +1803,7 @@ msgstr "5 хвилин"
 #: src/user-defined-types.md:12 src/methods-and-traits.md:8 src/modules.md:11
 #: src/concurrency/welcome.md:18 src/concurrency/threads.md:7
 #: src/concurrency/threads.md:8 src/concurrency/shared-state.md:8
-xmsgid "15 minutes"
+msgid "15 minutes"
 msgstr "15 хвилин"
 
 #: src/running-the-course/course-structure.md:17