8u GHA: Use GCC Major Version Dependencies Only

Major versions of GCC often cause problems with OpenJDK. Fedora's eager adoption of them means we often encounter these early. JDK-8282231 is just the latest example from the introduction of GCC 12.

However, the GHA workflow in OpenJDK doesn't just depend on a major version of GCC - which is actually contained in the Ubuntu package name of gcc-9 itself - but the full revision number, even down to local packaging changes.

I believe this is overkill and leads to valuable time being wasted on issues like JDK-8283778 where the GCC version itself didn't change at all, just the Ubuntu version suffix.

Rather than maintain this for 8u, I suggest we just depend on gcc-9 which is already a pretty modern version for 8u. I have yet to see an issue be specific to a minor GCC version bump, whereas the current setup is pretty much guaranteed to mean further fixes to the GitHub workflow every time the Ubuntu packager produces a new build.