Update dockerfile version to 26 (#6679)
Update dockerfile version to 26 (#6679)

Squash and merge as a safe commit - want to be a ble to build dockerfile early and prevent accumulating commits with an intermediate version.
nestlabs/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip,project-chip/connectedhomeip,nestlabs/connectedhomeip