Change error message in rustbook

Author: GuillaumeGomez

src/doc/trpl/casting-between-types.md

@@ -82,7 +82,7 @@ unsafe {
 with:
 
 ```text
-error: transmute called on types with different sizes: [u8; 4] (32 bits) to u64
+error: transmute called with differently sized types: [u8; 4] (32 bits) to u64
 (64 bits)
 ```
 

src/test/compile-fail/packed-struct-generic-transmute.rs

@@ -13,7 +13,7 @@
 // the error points to the start of the file, not the line with the
 // transmute
 
-// error-pattern: transmute called on types with different size
+// error-pattern: transmute called with differently sized types
 
 use std::mem;
 

src/test/compile-fail/packed-struct-transmute.rs

@@ -13,7 +13,7 @@
 // the error points to the start of the file, not the line with the
 // transmute
 
-// error-pattern: transmute called on types with different size
+// error-pattern: transmute called with differently sized types
 
 use std::mem;
 

src/test/compile-fail/transmute-different-sizes.rs

@@ -16,12 +16,12 @@ use std::mem::transmute;
 
 unsafe fn f() {
     let _: i8 = transmute(16i16);
-    //~^ ERROR transmute called on types with different sizes
+    //~^ ERROR transmute called with differently sized types
 }
 
 unsafe fn g<T>(x: &T) {
     let _: i8 = transmute(x);
-    //~^ ERROR transmute called on types with potentially different sizes
+    //~^ ERROR transmute called with differently sized types
 }
 
 fn main() {}