Merge pull request #1239 from rylev/regex-to-stable

Move `regex` to stable category

Author: rylev

collector/benchmarks/regex/perf-config.json

@@ -1,4 +1,4 @@
 {
     "touch_file": "src/lib.rs",
-    "category": "primary-and-stable"
-}
+    "category": "stable"
+}