Bump minimum browser versions

This change bumps out minimum supported browser versions just enough
so we can drop support for output transpilation via babel.

chrome: 74 -> 85
firefox: 68 -> 79
safari: 12.2 -> 14.1

This also means we always support the MUTABLE_GLOBALS and PROMISE_ANY
features, since its no longer possible to target engines without it.

Author: sbc100

ChangeLog.md

@@ -20,6 +20,15 @@ See docs/process.md for more on how version tagging works.
 
 5.0.8 (in development)
 ----------------------
+- The minimum versions of browser engines supported by emscripten generated
+  code was bumped, allowing us to remove our internal support for transpilation
+  via babel:
+    MIN_CHROME_VERSION: 74 -> 85
+    MIN_FIREFOX_VERSION: 68 -> 79
+    MIN_SAFARI_VERSION: 12.2 -> 14.1
+  This allows us to assume that features such as mutable-globals, and sign-ext,
+  and threading, are universally available and disabling these is no longer
+  possible.
 
 5.0.7 - 04/30/26
 ----------------