Update dependency com.google.code.gson:gson to v2.9.0

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
com.google.code.gson:gson	2.8.9 -> 2.9.0

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Release Notes

google/gson

### [`v2.9.0`](https://togithub.com/google/gson/blob/HEAD/CHANGELOG.md#Version-290) **The minimum supported Java version changes from 6 to 7.** - Change target Java version to 7 ([#​2043](https://togithub.com/google/gson/issues/2043)) - Put `module-info.class` into Multi-Release JAR folder ([#​2013](https://togithub.com/google/gson/issues/2013)) - Improve error message when abstract class cannot be constructed ([#​1814](https://togithub.com/google/gson/issues/1814)) - Support EnumMap deserialization ([#​2071](https://togithub.com/google/gson/issues/2071)) - Add LazilyParsedNumber default adapter ([#​2060](https://togithub.com/google/gson/issues/2060)) - Fix JsonReader.hasNext() returning true at end of document ([#​2061](https://togithub.com/google/gson/issues/2061)) - Remove Gradle build support. Build script was outdated and not actively maintained anymore ([#​2063](https://togithub.com/google/gson/issues/2063)) - Add `GsonBuilder.disableJdkUnsafe()` ([#​1904](https://togithub.com/google/gson/issues/1904)) - Add `UPPER_CASE_WITH_UNDERSCORES` in FieldNamingPolicy ([#​2024](https://togithub.com/google/gson/issues/2024)) - Fix failing to serialize Collection or Map with inaccessible constructor ([#​1902](https://togithub.com/google/gson/issues/1902)) - Improve TreeTypeAdapter thread-safety ([#​1976](https://togithub.com/google/gson/issues/1976)) - Fix `Gson.newJsonWriter` ignoring lenient and HTML-safe setting ([#​1989](https://togithub.com/google/gson/issues/1989)) - Delete unused LinkedHashTreeMap ([#​1992](https://togithub.com/google/gson/issues/1992)) - Make default adapters stricter; improve exception messages ([#​2000](https://togithub.com/google/gson/issues/2000)) - Fix `FieldNamingPolicy.upperCaseFirstLetter` uppercasing non-letter ([#​2004](https://togithub.com/google/gson/issues/2004))

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