Change fastlane full description from HTML to plain text

because F-Droid website and client will insert <br> elements
whenever there is a line break, resulting in ugly and invalid HTML.
See <https://gitlab.com/fdroid/fdroid-website/-/issues/247#note_825610220>.

Author: yawnoc

fastlane/metadata/android/en-US/full_description.txt

@@ -1,13 +1,16 @@
-<p>This keyboard app lets you input Chinese characters by typing stroke sequences (e.g. 天 is ㇐㇐㇒㇔).</p>
-<p>It is a minimalist implementation with the following features:</p>
-<ul>
-  <li>Good character support (over 28k characters) including vernacular Cantonese</li>
-  <li>User preference for traditional or simplified characters</li>
-  <li>No ads</li>
-  <li>No permissions</li>
-  <li>No tracking or telemetry</li>
-  <li>Deterministic candidate generation which doesn't learn user input</li>
-</ul>
-<p>After installing the app, launch and follow the prompts to enable Stroke Input Method in your system settings. There will be a default warning shown — this is normal.</p>
-<p>This app is free and open-source software, licensed under the GNU General Public License v3.0 (GPL-3.0-only).</p>
-<p>You are welcome and encouraged to inspect the source code: <a href="https://github.com/stroke-input/stroke-input-android">https://github.com/stroke-input/stroke-input-android</a></p>
+This keyboard app lets you input Chinese characters by typing stroke sequences (e.g. 天 is ㇐㇐㇒㇔).
+
+It is a minimalist implementation with the following features:
+
+* Good character support (over 28k characters) including vernacular Cantonese
+* User preference for traditional or simplified characters
+* No ads
+* No permissions
+* No tracking or telemetry
+* Deterministic candidate generation which doesn't learn user input
+
+After installing the app, launch and follow the prompts to enable Stroke Input Method in your system settings. There will be a default warning shown — this is normal.
+
+This app is free and open-source software, licensed under the GNU General Public License v3.0 (GPL-3.0-only).
+
+You are welcome and encouraged to inspect the source code: https://github.com/stroke-input/stroke-input-android