Update gradle properties for 6.6.0 (#263)

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gradle.properties

@@ -1,5 +1,5 @@
 group=com.nylas.sdk
-version=2.5.2
+version=2.6.0
 
 # Override and set these in ~/.gradle/gradle.properties
 ossrhUser=
@@ -11,4 +11,4 @@ signing.secretKeyRingFile=~/.gnupg/secring.gpg
 # 2020-04-27 - workaround for https://issues.sonatype.org/browse/NEXUS-21802
 # PLEASE CHECK once in awhile to see if this issue is resolved
 # and this flag can be removed to improve the security of release checksums
-systemProp.org.gradle.internal.publish.checksums.insecure=true
+systemProp.org.gradle.internal.publish.checksums.insecure=true