Adapt in-memory size check to Rust 1.65 and below

Rust 1.65 reduces size in memory, and to maintain compatibility with
older compilers, let's just assure we don't grow without us knowning.

Author: Byron

git-diff/src/tree/visit.rs

@@ -78,10 +78,11 @@ mod tests {
 
     #[test]
     fn size_of_change() {
-        assert_eq!(
-            std::mem::size_of::<Change>(),
-            46,
-            "this type shouldn't grow without us knowing"
+        let actual = std::mem::size_of::<Change>();
+        assert!(
+            actual <= 46,
+            "{} <= 46: this type shouldn't grow without us knowing",
+            actual
         )
     }
 }

git-object/tests/object.rs

@@ -30,9 +30,10 @@ fn fixture_bytes(path: &str) -> Vec<u8> {
 
 #[test]
 fn size_in_memory() {
-    assert_eq!(
-        std::mem::size_of::<git_object::Object>(),
-        264,
-        "Prevent unexpected growth of what should be lightweight objects"
+    let actual = std::mem::size_of::<git_object::Object>();
+    assert!(
+        actual <= 264,
+        "{} <= 264: Prevent unexpected growth of what should be lightweight objects",
+        actual
     )
 }