fix(deps): update bouncycastle to v1.78

Author: renovate[bot]

sigstore-java/build.gradle.kts

@@ -35,8 +35,8 @@ dependencies {
 
     implementation("commons-codec:commons-codec:1.16.1")
     implementation("com.google.code.gson:gson:2.10.1")
-    implementation("org.bouncycastle:bcutil-jdk18on:1.77")
-    implementation("org.bouncycastle:bcpkix-jdk18on:1.77")
+    implementation("org.bouncycastle:bcutil-jdk18on:1.78")
+    implementation("org.bouncycastle:bcpkix-jdk18on:1.78")
 
     implementation(platform("com.google.oauth-client:google-oauth-client-bom:1.35.0"))
     implementation("com.google.oauth-client:google-oauth-client")