build(deps): update dependency com.google.cloud:google-cloud-shared-config to v1.2.6 (#682)

[![WhiteSource Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-shared-config](https://github.com/googleapis/java-shared-config) | `1.2.5` -> `1.2.6` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-shared-config/1.2.6/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-shared-config/1.2.6/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-shared-config/1.2.6/compatibility-slim/1.2.5)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-shared-config/1.2.6/confidence-slim/1.2.5)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

<details>
<summary>googleapis/java-shared-config</summary>

### [`v1.2.6`](https://github.com/googleapis/java-shared-config/blob/HEAD/CHANGELOG.md#&#8203;126-httpsgithubcomgoogleapisjava-shared-configcomparev125v126-2022-01-19)

[Compare Source](https://github.com/googleapis/java-shared-config/compare/v1.2.5...v1.2.6)

</details>

---

### Configuration

📅 **Schedule**: At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, click this checkbox.

---

This PR has been generated by [WhiteSource Renovate](https://renovate.whitesourcesoftware.com). View repository job log [here](https://app.renovatebot.com/dashboard#github/googleapis/java-core).

Author: renovate-bot

google-cloud-core-bom/pom.xml

@@ -8,7 +8,7 @@
   <parent>
     <groupId>com.google.cloud</groupId>
     <artifactId>google-cloud-shared-config</artifactId>
-    <version>1.2.5</version>
+    <version>1.2.6</version>
   </parent>
 
   <name>Google Cloud Core</name>

pom.xml

@@ -14,7 +14,7 @@
   <parent>
     <groupId>com.google.cloud</groupId>
     <artifactId>google-cloud-shared-config</artifactId>
-    <version>1.2.5</version>
+    <version>1.2.6</version>
   </parent>
 
   <developers>