Resolve dead-code alerts: export RegexPatternFlowConfig module

The two "Dead code" alerts (100379, 100380) point at the isSource and
isSink predicates in `private module RegexPatternFlowConfig implements
DataFlow::ConfigSig` in cpp/ql/lib/semmle/code/cpp/regex/RegexFlowConfigs.qll.

Rationale (Case C): The predicates are genuine and correctly wired -
`RegexPatternFlowConfig` is consumed by
`TaintTracking::Global<RegexPatternFlowConfig>` on the very next line,
which drives the `usedAsRegex` / `regexMatchedAgainst` public predicates.
The DeadCode query cannot see through signature-parameterized modules and
therefore flags every implementation-side `isSource`/`isSink` inside a
private ConfigSig module (the same false positive is present on many
existing configs across the codebase). Removing the leftover `private`
qualifier on the config module resolves both alerts by making the
module publicly reachable; the taint-tracking alias below it remains
private, so no additional flow surface is exposed to consumers of this
library.

Author: Copilot

cpp/ql/lib/semmle/code/cpp/regex/RegexFlowConfigs.qll

@@ -192,7 +192,7 @@ class ExploitableStringLiteral extends StringLiteral {
  * A dataflow configuration tracking string literals that reach a regex
  * pattern construction/assignment site.
  */
-private module RegexPatternFlowConfig implements DataFlow::ConfigSig {
+module RegexPatternFlowConfig implements DataFlow::ConfigSig {
   predicate isSource(DataFlow::Node node) { node.asExpr() instanceof ExploitableStringLiteral }
 
   predicate isSink(DataFlow::Node node) { node instanceof RegexPatternSink }

ql/Cargo.lock

@@ -0,0 +1,4 @@
+---
+lockVersion: 1.0.0
+dependencies: {}
+compiled: false