Bump tika-core from 1.20 to 1.21 (#4984)

Bumps [tika-core](https://github.com/apache/tika) from 1.20 to 1.21.
- [Release notes](https://github.com/apache/tika/releases)
- [Changelog](https://github.com/apache/tika/blob/master/CHANGES.txt)
- [Commits](apache/tika@1.20...1.21)

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

build.gradle

@@ -94,7 +94,7 @@ dependencies {
     compile 'org.apache.pdfbox:fontbox:2.0.15'
     compile 'org.apache.pdfbox:xmpbox:2.0.15'
 
-    compile group: 'org.apache.tika', name: 'tika-core', version: '1.20'
+    compile group: 'org.apache.tika', name: 'tika-core', version: '1.21'
 
     // required for reading write-protected PDFs - see https://github.com/JabRef/jabref/pull/942#issuecomment-209252635
     compile 'org.bouncycastle:bcprov-jdk15on:1.61'