[frogr] Use meson's "warning_level" build option instead of "warnlevel"

[Mario Sanchez Prada <msanchez src gnome org>]

commit 623d7e397baff3a8ab1695e190b13bc60153b64c
Author: Mario Sanchez Prada <msanchez gnome org>
Date:   Mon Dec 7 22:26:34 2020 +0100

    Use meson's "warning_level" build option instead of "warnlevel"
    
    The correct option's name is "warning_level", so change it for it
    to actually be effective while building.

 meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index 37f76d7..87e4de3 100644
--- a/meson.build
+++ b/meson.build
@@ -2,7 +2,7 @@ project('frogr', 'c',
         version: '1.7',
         license: 'GPL3',
         default_options: [
-            'warnlevel=2',
+            'warning_level=2',
             'werror=false'
         ])