Bump Bouncy Castle to 1.78.1

1.78 had broken OSGi metadata; this was fixed in 1.78.1.
diff --git a/pom.xml b/pom.xml
index 0376915..34571fc 100644
--- a/pom.xml
+++ b/pom.xml
@@ -105,7 +105,7 @@
 
         <min.required.maven.version>3.5.0</min.required.maven.version>
         <groovy.version>4.0.17</groovy.version>
-        <bouncycastle.version>1.77</bouncycastle.version>
+        <bouncycastle.version>1.78.1</bouncycastle.version>
             <!-- NOTE: upgrading slf4j beyond this version causes
             
             Execution verify-style of goal org.apache.maven.plugins:maven-checkstyle-plugin:3.1.2:check failed.: NullPointerException