Attempt to update OSGi metadata for JSpecify annotations.

The original OSGi metadata was added back in 53abadc, at which point it mentioned `javax.annotation`.

Since then, we've added and removed various annotation dependencies, apparently without ill effects. (And when we tried to make a change that clearly _did_ require a change to the metadata in cl/103098597, we apparently got an error.) So it's possible that listing annotations has _never_ been necessary or at least that it became unnecessary in the 3.5 years between those two prior changes. Or maybe none of our users both use OSGi and try to read our nullness annotations (but if they did, they'd have problems)?

Anyway, if listing annotations _is_ important, then we should probably be doing it for the Error Prone and J2ObjC annotations, too.... But for some reason, when I was [replying to an comment that mentioned OSGi on the Jackson issue tracker](FasterXML/jackson-future-ideas#87 (reply in thread)), I decided that it was worth dipping my toes in here, and I guess I figured I'd start small.

RELNOTES=Listed the JSpecify annotations as an optional dependency in our OSGi metadata.
PiperOrigin-RevId: 768209312

Author: cpovirk

android/guava/pom.xml

@@ -96,7 +96,7 @@
             </Export-Package>
             <Import-Package>
               com.google.common.util.concurrent.internal,
-              javax.annotation;resolution:=optional,
+              org.jspecify.annotations;resolution:=optional,
               javax.crypto.*;resolution:=optional,
               sun.misc.*;resolution:=optional
             </Import-Package>

guava/pom.xml

@@ -89,7 +89,7 @@
             </Export-Package>
             <Import-Package>
               com.google.common.util.concurrent.internal,
-              javax.annotation;resolution:=optional,
+              org.jspecify.annotations;resolution:=optional,
               javax.crypto.*;resolution:=optional,
               sun.misc.*;resolution:=optional
             </Import-Package>