refactor: iostream.h renamed to ostream.h

docs/getting_started/code_example.md

@@ -39,7 +39,7 @@ performed without sacrificing accuracy. Please see the below example for a quick
 
 ```cpp
 #include <mp-units/format.h>
-#include <mp-units/iostream.h>
+#include <mp-units/ostream.h>
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/si.h>
@@ -76,7 +76,7 @@ int main()
 }
 ```
 
-!!! example "[Try it on Compiler Explorer](https://godbolt.org/z/T8bovrqTP)"
+!!! example "[Try it on Compiler Explorer](https://godbolt.org/z/3q646qrb3)"
 
 !!! note