docs(cli/dts): fix link from master to main (denoland#10633)

cli/dts/lib.deno.unstable.d.ts

@@ -143,7 +143,7 @@ declare namespace Deno {
    *
    * The plugin system is not stable and will change in the future, hence the
    * lack of docs. For now take a look at the example
-   * https://github.com/denoland/deno/tree/master/test_plugin
+   * https://github.com/denoland/deno/tree/main/test_plugin
    */
   export function openPlugin(filename: string): number;
 

cli/lsp/language_server.rs

@@ -2960,7 +2960,7 @@ mod tests {
                 "language": "typescript",
                 "value": "function Deno.openPlugin(filename: string): number"
               },
-              "**UNSTABLE**: new API, yet to be vetted.\n\nOpen and initialize a plugin.\n\n```ts\nconst rid = Deno.openPlugin(\"./path/to/some/plugin.so\");\nconst opId = Deno.core.ops()[\"some_op\"];\nconst response = Deno.core.dispatch(opId, new Uint8Array([1,2,3,4]));\nconsole.log(`Response from plugin ${response}`);\n```\n\nRequires `allow-plugin` permission.\n\nThe plugin system is not stable and will change in the future, hence the\nlack of docs. For now take a look at the example\nhttps://github.com/denoland/deno/tree/master/test_plugin"
+              "**UNSTABLE**: new API, yet to be vetted.\n\nOpen and initialize a plugin.\n\n```ts\nconst rid = Deno.openPlugin(\"./path/to/some/plugin.so\");\nconst opId = Deno.core.ops()[\"some_op\"];\nconst response = Deno.core.dispatch(opId, new Uint8Array([1,2,3,4]));\nconsole.log(`Response from plugin ${response}`);\n```\n\nRequires `allow-plugin` permission.\n\nThe plugin system is not stable and will change in the future, hence the\nlack of docs. For now take a look at the example\nhttps://github.com/denoland/deno/tree/main/test_plugin"
             ],
             "range": {
               "start": {