Upgrade Error Prone 2.25.0 -> 2.26.1 (#1078)

See:
- https://github.com/google/error-prone/releases/tag/v2.26.0
- https://github.com/google/error-prone/releases/tag/v2.26.1
- google/error-prone@v2.25.0...v2.26.1
- PicnicSupermarket/error-prone@v2.25.0-picnic-2...v2.26.1-picnic-1

pom.xml

@@ -207,8 +207,8 @@
         <version.auto-service>1.1.1</version.auto-service>
         <version.auto-value>1.10.4</version.auto-value>
         <version.error-prone>${version.error-prone-orig}</version.error-prone>
-        <version.error-prone-fork>v${version.error-prone-orig}-picnic-2</version.error-prone-fork>
-        <version.error-prone-orig>2.25.0</version.error-prone-orig>
+        <version.error-prone-fork>v${version.error-prone-orig}-picnic-1</version.error-prone-fork>
+        <version.error-prone-orig>2.26.1</version.error-prone-orig>
         <version.error-prone-slf4j>0.1.22</version.error-prone-slf4j>
         <version.guava-beta-checker>1.0</version.guava-beta-checker>
         <version.jdk>17</version.jdk>