RFR: 8257194: Add 'foreign linker API' in 'jdk.incubator.foreign' module desc/summary

[Maurizio Cimadamore]

This simple patch updates the jaavdoc in the module-info file of jdk.incubator.foreign to reflect the fact that support of foreign function calls has been added.

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Commit messages:
 - Fix module-info javadoc

Changes: https://git.openjdk.java.net/jdk/pull/1671/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1671&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257194
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1671.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1671/head:pull/1671

PR: https://git.openjdk.java.net/jdk/pull/1671