meson: Update pest subproject family

Starting with Rust 1.83 this benign warning is show when compiling the pest dependency:

```
warning: elided lifetime has a name
   --> pest/src/iterators/pairs.rs:330:70
    |
89  | impl<'i, R: RuleType> Pairs<'i, R> {
    |      -- lifetime `'i` declared here
...
330 |     ) -> Filter<FlatPairs<'i, R>, impl FnMut(&Pair<'i, R>) -> bool + '_> {
    |                                                                      ^^ this elided lifetime gets resolved as `'i`
    |
    = note: `#[warn(elided_named_lifetimes)]` on by default
```

Meson, at least as of version 1.7.0, unfortunately does not suppress warnings originating in dependencies.
Upstream has resolved the warning in 2.8.0, so update to that.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34368>

subprojects/packagefiles/pest/meson.build

@@ -1,7 +1,7 @@
 project(
   'pest',
   'rust',
-  version : '2.7.11',
+  version : '2.8.0',
   license :'MIT OR Apache-2.0',
 )
 

subprojects/packagefiles/pest_derive/meson.build

@@ -1,7 +1,7 @@
 project(
   'pest_derive',
   'rust',
-  version : '2.7.11',
+  version : '2.8.0',
   license :'MIT OR Apache-2.0',
 )
 

subprojects/packagefiles/pest_generator/meson.build

@@ -1,7 +1,7 @@
 project(
   'pest_generator',
   'rust',
-  version : '2.7.11',
+  version : '2.8.0',
   license :'MIT OR Apache-2.0',
 )
 

subprojects/packagefiles/pest_meta/meson.build

@@ -1,7 +1,7 @@
 project(
   'pest_meta',
   'rust',
-  version : '2.7.11',
+  version : '2.8.0',
   license :'MIT OR Apache-2.0',
 )