[meson] move meson version so can be referenced easier

RELEASING.md

@@ -22,7 +22,7 @@ HarfBuzz release walk-through checklist:
 
 4. Make sure you have correct date and new version at the top of NEWS file,
 
-5. Bump version in configure.ac line 3 and meson.build line 4.
+5. Bump version in line 3 of meson.build and configure.ac.
 
 6. Do "make distcheck", if it passes, you get a tarball.
    Otherwise, fix things and commit them separately before making release,

meson.build

@@ -1,7 +1,8 @@
 project('harfbuzz', 'c', 'cpp',
   meson_version: '>= 0.53.0',
+  version: '2.6.8',
   default_options: ['cpp_std=c++11'],
-  version: '2.6.8')
+)
 
 warning('Meson is not our main build system for building *nix packages yet we encourage packagers to test it and give us feedback about it.')