ci: bump meson version in LGTM

ci: bump meson version in LGTM

Otherwise LGTM fails to detect the build system:

```
[2021-07-27 23:18:47] [build-stdout] The Meson build system
[2021-07-27 23:18:47] [build-stdout] Version: 0.51.2
[2021-07-27 23:18:47] [build-stdout] Source dir: /opt/src
[2021-07-27 23:18:47] [build-stdout] Build dir: /opt/src/_lgtm_build_dir
[2021-07-27 23:18:47] [build-stdout] Build type: native build
[2021-07-27 23:18:47] [build-stdout] meson.build:3:0: ERROR: Meson version is 0.51.2 but project requires >= 0.53.2
[2021-07-27 23:18:47] [build-stdout] A full log can be found at /opt/src/_lgtm_build_dir/meson-logs/meson-log.txt
```