chore: update dependency com.fasterxml.jackson:jackson-bom to v2.21.0 (googleapis#4069)

This PR contains the following updates:

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[com.fasterxml.jackson:jackson-bom](https://redirect.github.com/FasterXML/jackson-bom)
| `2.20.1` → `2.21.0` |
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|
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dependencies.txt

@@ -32,7 +32,7 @@ com.google.api-client:google-api-client,google.api-client=2.8.1
 org.threeten:threeten-extra,threeten-extra=1.8.0
 io.opencensus:opencensus-api,opencensus=0.31.1
 com.google.code.findbugs:jsr305,findbugs=3.0.2
-com.fasterxml.jackson:jackson-bom,jackson=2.20.1
+com.fasterxml.jackson:jackson-bom,jackson=2.21.0
 commons-codec:commons-codec,codec=1.20.0
 org.apache.httpcomponents:httpclient,httpcomponents.httpclient=4.5.14
 org.apache.httpcomponents:httpcore,httpcomponents.httpcore=4.4.16