doc: fix typo in doc/api/http2/md

PR-URL: #37479
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/http2.md

@@ -1444,7 +1444,7 @@ added: v8.4.0
 changes:
   - version: v14.5.0
     pr-url: https://github.com/nodejs/node/pull/33160
-    description: Allow explicity setting date headers.
+    description: Allow explicitly setting date headers.
 -->
 
 * `headers` {HTTP/2 Headers Object}
@@ -1491,7 +1491,7 @@ added: v8.4.0
 changes:
   - version: v14.5.0
     pr-url: https://github.com/nodejs/node/pull/33160
-    description: Allow explicity setting date headers.
+    description: Allow explicitly setting date headers.
   - version: v12.12.0
     pr-url: https://github.com/nodejs/node/pull/29876
     description: The `fd` option may now be a `FileHandle`.
@@ -1592,7 +1592,7 @@ added: v8.4.0
 changes:
   - version: v14.5.0
     pr-url: https://github.com/nodejs/node/pull/33160
-    description: Allow explicity setting date headers.
+    description: Allow explicitly setting date headers.
   - version: v10.0.0
     pr-url: https://github.com/nodejs/node/pull/18936
     description: Any readable file, not necessarily a