chore: updated the contributing.md

Author: aryamohanan

CONTRIBUTING.md

@@ -376,16 +376,9 @@ We have added the ESM support for all Node.js versions, Since version 20.6, [ESM
 
 Use the following command to enable experimental ESM support:
 
-- For Node.js versions greater than or equal to 18.19:
-
 ```sh
 node --import  /path/to/instana/node_modules/@instana/collector/esm-register.mjs entry-point
 ```
-- For Node.js versions less than 18.19:
-
-```sh
-node --experimental-loader /path/to/instana/node_modules/@instana/collector/esm-loader.mjs entry-point
-```
 
 ## Node.js prerelease
 

packages/core/src/tracing/instrumentation/protocols/nativeFetch.js

@@ -33,8 +33,7 @@ let isActive = false;
 exports.shouldAddHeadersToOptionsUnconditionally = function () {
   return (
     semver.eq(process.version, '21.0.0') ||
-    (semver.gte(process.version, '20.8.1') && semver.lt(process.version, '20.10.0')) ||
-    (semver.gte(process.version, '18.18.2') && semver.lt(process.version, '18.19.0'))
+    (semver.gte(process.version, '20.8.1') && semver.lt(process.version, '20.10.0'))
   );
 };