meson: Fix stdplus_dep name

Change-Id: I6c48802b2aeed0b72b2ed4d9a9a4dbf0dec9cf57
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/meson.build b/src/meson.build
index 29877dd..a9fbc6c 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -21,7 +21,7 @@
 
 sdeventplus_deps = [
   dependency('libsystemd', version: '>=240'),
-  dependency('stdplus', fallback: ['stdplus', 'stdplus']),
+  dependency('stdplus', fallback: ['stdplus', 'stdplus_dep']),
   function2_dep,
 ]