Update the VSCode language from upstream

This updates to
wooorm/markdown-tm-language@5caa71e

Closes #480

packages/vscode-mdx/syntaxes/source.mdx.tmLanguage

@@ -7,7 +7,7 @@
  Once accepted there, it can be pulled into this project (`vscode-mdx`) with
  `script/generate.mjs`, and released.
 
- Version from SHA: 403f851b6ff7b52f3dbf5fc3b3e5b215c8e505a2.
+ Version from SHA: 5caa71e2bbddea59b27c6a5a346881cd10fa0f5f.
  -->
  <dict>
  <key>fileTypes</key>
@@ -2330,7 +2330,7 @@
  <key>extension-mdx-expression-flow</key>
  <dict>
  <key>begin</key>
- <string>(?:^|\G)[\t ]*(\{)</string>
+ <string>(?:^|\G)[\t ]*(\{)(?!.*\}[\t ]*.)</string>
  <key>beginCaptures</key>
  <dict>
  <key>1</key>