tools: fix typo in postmortem generator

BUG=
R=machenbach

Review URL: https://codereview.chromium.org/1439763002

Cr-Commit-Position: refs/heads/master@{#31961}

tools/gen-postmortem-metadata.py

@@ -168,7 +168,7 @@ consts_misc = [
     { 'name': 'scopeinfo_idx_ncontextlocals',
         'value': 'ScopeInfo::kContextLocalCount' },
     { 'name': 'scopeinfo_idx_ncontextglobals',
-        'value': 'ScopeInfo::kContextLocalCount' },
+        'value': 'ScopeInfo::kContextGlobalCount' },
     { 'name': 'scopeinfo_idx_first_vars',
         'value': 'ScopeInfo::kVariablePartIndex' },