graphql: Fix curl invocation

curl does not support separating long options and their values by an
equals sign (only by spaces), see curl(1):
	https://curl.se/docs/manpage.html

graphql.md

@@ -98,7 +98,7 @@ Here is a simple request:
 ```sh
 oauth_token=your oauth token
 curl \
-  --oauth2-bearer="$oauth_token" \
+  --oauth2-bearer "$oauth_token" \
   -H 'Content-Type: application/json' \
   -d '{"query": "{ version { major, minor, patch } }"}' \
   https://meta.sr.ht/query