docs(readme): flip stale PMPL-1.0 license badge to MPL-2.0 (#33)

Single-line README badge polish.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

README.adoc

@@ -1,4 +1,4 @@
-image:https://img.shields.io/badge/License-PMPL--1.0-blue.svg[License: PMPL-1.0,link="https://github.com/hyperpolymath/palimpsest-license"]
+image:https://img.shields.io/badge/License-MPL--2.0-blue.svg[License: MPL-2.0,link="https://www.mozilla.org/MPL/2.0/"]
 // SPDX-License-Identifier: MPL-2.0
 // SPDX-FileCopyrightText: 2025 hyperpolymath
 
@@ -21,7 +21,7 @@ Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>
 image:https://img.shields.io/badge/RSR-Certified-gold[RSR Certified,link=https://github.com/hyperpolymath/rhodium-standard-repositories]
 image:https://img.shields.io/badge/Status-Specification-orange[Status: Specification]
 image:https://img.shields.io/badge/Version-0.1.0-blue[Version 0.1.0]
-image:https://img.shields.io/badge/License-PMPL--1.0-blue.svg[License: PMPL-1.0,link="https://github.com/hyperpolymath/palimpsest-license"]
+image:https://img.shields.io/badge/License-MPL--2.0-blue.svg[License: MPL-2.0,link="https://www.mozilla.org/MPL/2.0/"]
 
 toc::[]