Bump flexmark-ext-gfm-tasklist from 0.61.16 to 0.61.20 (#6364)

Bumps [flexmark-ext-gfm-tasklist](https://github.com/vsch/flexmark-java) from 0.61.16 to 0.61.20.
- [Release notes](https://github.com/vsch/flexmark-java/releases)
- [Commits](vsch/flexmark-java@0.61.16...0.61.20)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

build.gradle

@@ -198,7 +198,7 @@ dependencies {
 
     implementation 'com.vladsch.flexmark:flexmark:0.61.20'
     implementation 'com.vladsch.flexmark:flexmark-ext-gfm-strikethrough:0.61.6'
-    implementation 'com.vladsch.flexmark:flexmark-ext-gfm-tasklist:0.61.16'
+    implementation 'com.vladsch.flexmark:flexmark-ext-gfm-tasklist:0.61.20'
 
     testImplementation 'io.github.classgraph:classgraph:4.8.77'
     testImplementation 'org.junit.jupiter:junit-jupiter:5.6.2'