fix: use values that are representable as double in test

This should fix a [test failure on i386][1]:

```
lrutest: ./dune/common/test/lrutest.cc:29: void lru_test(): Assertion `lru.front() == 1.3 && lru.back() == 2.0' failed.
```

  [1]: https://buildd.debian.org/status/fetch.php?pkg=dune-common&arch=i386&ver=2.9.0-5&stamp=1703605683&raw=0

dune/common/test/lrutest.cc

@@ -20,7 +20,7 @@ void lru_test()
   lru.insert(11, 2.0);
   assert(lru.front() == 2.0 && lru.back() == 1.0);
   lru.insert(12, 99);
-  lru.insert(13, 1.3);
+  lru.insert(13, 1.125);
   lru.insert(14, 12345);
   lru.insert(15, -17);
   assert(lru.front() == -17 && lru.back() == 1.0);
@@ -29,7 +29,7 @@ void lru_test()
   assert(lru.front() == 1.0 && lru.back() == 2.0);
   // update
   lru.touch(13);
-  assert(lru.front() == 1.3 && lru.back() == 2.0);
+  assert(lru.front() == 1.125 && lru.back() == 2.0);
   // remove item
   lru.pop_front();
   assert(lru.front() == 1.0 && lru.back() == 2.0);