Fix memory leak in SourceManager.verifiedPaths.

(cherry picked from commit 1eb663808c9ba1b80bc2f1bb5ad9d09e87bbc50e)

Adapted to community code that uses HashMap instead of ConcurrrentHashMap

Author: christianhaeubl

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/sources/SourceManager.java

@@ -160,7 +160,7 @@ private static Path computePrototypeName(String fileName, String packageName) {
      * A map from a Java type to an associated source paths which is known to have an up to date
      * entry in the relevant source file cache. This is used to memoize previous lookups.
      */
-    private static HashMap<ResolvedJavaType, Path> verifiedPaths = new HashMap<>();
+    private HashMap<ResolvedJavaType, Path> verifiedPaths = new HashMap<>();
 
     /**
      * An invalid path used as a marker to track failed lookups so we don't waste time looking up