fix(flavor): use main branch for limit-req-rw module

Switched ngx-http-limit-req-rw-module from the 'read-write-fix' branch to
the 'main' branch in flavors.json. This ensures compatibility with the
latest upstream changes and simplifies future updates.

Author: ravilock

flavors.json

@@ -9,7 +9,7 @@
         "https://github.com/openresty/echo-nginx-module.git",
         "https://github.com/openresty/headers-more-nginx-module.git",
         "https://github.com/tsuru/ngx-location-name-module.git:main",
-        "https://github.com/tsuru/ngx-http-limit-req-rw-module.git:read-write-fix",
+        "https://github.com/tsuru/ngx-http-limit-req-rw-module.git:main",
         "https://github.com/FRiCKLE/ngx_cache_purge.git:pr-45",
         "https://github.com/wandenberg/nginx-push-stream-module.git",
         "https://github.com/vozlt/nginx-module-vts.git:v0.2.4",