Update LJM for taking the changes for capScreenshareBitrate

package-lock.json

       }
     },
     "lib-jitsi-meet": {
-      "version": "github:jitsi/lib-jitsi-meet#cdd2029b4b6b3626658f9834c324e1ffb7474795",
-      "from": "github:jitsi/lib-jitsi-meet#cdd2029b4b6b3626658f9834c324e1ffb7474795",
+      "version": "github:jitsi/lib-jitsi-meet#a6fd643e060dc63833ce2d291903b8233202a90d",
+      "from": "github:jitsi/lib-jitsi-meet#a6fd643e060dc63833ce2d291903b8233202a90d",
       "requires": {
         "@jitsi/sdp-interop": "0.1.14",
         "@jitsi/sdp-simulcast": "0.2.2",

package.json

     "js-utils": "github:jitsi/js-utils#192b1c996e8c05530eb1f19e82a31069c3021e31",
     "jsrsasign": "8.0.12",
     "jwt-decode": "2.2.0",
-    "lib-jitsi-meet": "github:jitsi/lib-jitsi-meet#cdd2029b4b6b3626658f9834c324e1ffb7474795",
+    "lib-jitsi-meet": "github:jitsi/lib-jitsi-meet#a6fd643e060dc63833ce2d291903b8233202a90d",
     "libflacjs": "github:mmig/libflac.js#93d37e7f811f01cf7d8b6a603e38bd3c3810907d",
     "lodash": "4.17.13",
     "moment": "2.19.4",