Bump bcprov-jdk15on from 1.60 to 1.61 (#4653)

Bumps [bcprov-jdk15on](https://github.com/bcgit/bc-java) from 1.60 to 1.61.
- [Release notes](https://github.com/bcgit/bc-java/releases)
- [Changelog](https://github.com/bcgit/bc-java/blob/master/docs/releasenotes.html)
- [Commits](https://github.com/bcgit/bc-java/commits)

Signed-off-by: dependabot[bot] <support@dependabot.com>

build.gradle

@@ -102,7 +102,7 @@ dependencies {
     compile group: 'org.apache.tika', name: 'tika-core', version: '1.20'
 
     // required for reading write-protected PDFs - see https://github.com/JabRef/jabref/pull/942#issuecomment-209252635
-    compile 'org.bouncycastle:bcprov-jdk15on:1.60'
+    compile 'org.bouncycastle:bcprov-jdk15on:1.61'
 
     compile 'commons-cli:commons-cli:1.4'