Remove stateInline.labelUnmatchedScopes

looks like a dead code

lib/helpers/parse_link_label.js

@@ -11,11 +11,6 @@ module.exports = function parseLinkLabel(state, start, disableNested) {
       max = state.posMax,
       oldPos = state.pos;
 
-  if (state.labelUnmatchedScopes) {
-    state.labelUnmatchedScopes--;
-    return -1;
-  }
-
   state.pos = start + 1;
   level = 1;
 
@@ -44,9 +39,6 @@ module.exports = function parseLinkLabel(state, start, disableNested) {
 
   if (found) {
     labelEnd = state.pos;
-    state.labelUnmatchedScopes = 0;
-  } else {
-    state.labelUnmatchedScopes = level - 1;
   }
 
   // restore old state

lib/rules_inline/state_inline.js

@@ -17,11 +17,6 @@ function StateInline(src, md, env, outTokens) {
 
   this.cache = [];        // Stores { start: end } pairs. Useful for backtrack
                           // optimization of pairs parse (emphasis, strikes).
-
-  // Link parser state vars
-
-  this.labelUnmatchedScopes = 0; // Track unpaired `[` for link labels
-                                 // (backtrack optimization)
 }