meson: Rename stdplus to stdplus_dep

This is the convention that meson builds should conform to.

Change-Id: Ia1a7e1a55e32200adbe37fa75ce02aee34df0219
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/meson.build b/test/meson.build
index 9a9b060..4e7f2b6 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -45,7 +45,7 @@
     test(t, executable(t.underscorify(), t + '.cpp',
                        build_by_default: false,
                        implicit_include_directories: false,
-                       dependencies: [stdplus, gtest, gmock]))
+                       dependencies: [stdplus_dep, gtest, gmock]))
   endforeach
 endif
 
@@ -102,6 +102,6 @@
     test(t, executable(t.underscorify(), t + '.cpp',
                        build_by_default: false,
                        implicit_include_directories: false,
-                       dependencies: [stdplus, span_dep, catch2]))
+                       dependencies: [stdplus_dep, catch2]))
   endforeach
 endif