build: lower meson requirement and fix warning

meson.build

 project('libinputsynth', 'c', version: '0.11.0',
-  meson_version: '>= 0.50.0',
+  meson_version: '>= 0.45.1',
 )
 
 

src/meson.build

@@ -17,7 +17,6 @@ configure_file(
   input: 'inputsynth-version.h.in',
   output: 'inputsynth-version.h',
   configuration: version_conf,
-  install: true,
   install_dir: join_paths(get_option('includedir'), api_path)
 )