Update CONTRIBUTING.md for java 17
Looks like building the new Spring instrumentation requires java 17+,
right?
@@ -8,7 +8,7 @@ and discuss your ideas or propose the changes you wish to make.
## Building
-In order to build and test this whole repository you need JDK 11+.
+In order to build and test this whole repository you need JDK 17 or higher.
Some instrumentations and tests may put constraints on which java versions they support.
See [Running the tests](./docs/contributing/running-tests.md) for more details.
