build: failing "with-external-deps" CI job

Problem:
Since 20edb8fa9a, generating helptags requires the
`tree-sitter-vimdoc` parser, but the external_deps CI job builds with
USE_BUNDLED_TS_PARSERS disabled.

Solution:
Set USE_BUNDLED_TS_PARSERS.

cmake.deps/CMakePresets.json

@@ -17,6 +17,7 @@
       "cacheVariables": {
         "USE_BUNDLED":"OFF",
         "USE_BUNDLED_TS":"ON",
+        "USE_BUNDLED_TS_PARSERS":"ON",
         "USE_BUNDLED_UTF8PROC":"ON",
         "ENABLE_WASMTIME":"OFF"
       },