[CRX] Bump minimum_chrome_version from 88 to 103

The minimum required version is Chrome 103 because wildcard support for
web_accessible_resources[].extension_id was introduced in 103, in
https://chromium.googlesource.com/chromium/src/+/c9caeb1a080f165f48d2a90559aa35d22965b440

A way to broaden compatibility is to drop that key. By doing so, the
minimum required Chrome version is then 96, because of the
chrome.storage.session API (and declarativeNetRequestWithHostAccess).

Since gulpfile.js already defines "Chrome >= 98" and there is no real
point in expanding support to older versions, I'm just setting the
minimum version to 103.

extensions/chromium/manifest.json

@@ -1,5 +1,5 @@
 {
-  "minimum_chrome_version": "88",
+  "minimum_chrome_version": "103",
   "manifest_version": 3,
   "name": "PDF Viewer",
   "version": "PDFJSSCRIPT_VERSION",