x11/gnome-shell: unbreak build with Meson 0.61.0

subprojects/extensions-tool/src/templates/meson.build:7:2: ERROR: Function does not take positional arguments.
subprojects/extensions-app/data/meson.build:17:5: ERROR: Function does not take positional arguments.
subprojects/extensions-app/data/metainfo/meson.build:2:5: ERROR: Function does not take positional arguments.
[...]

PR: 260943
Regressed by: https://github.com/mesonbuild/meson/commit/61f2866a9fa1