[editorial] Add space in schemas/overview (#2351)

For context, see https:/open-telemetry/opentelemetry-specification/pull/2320/files#r807334158

specification/schemas/overview.md

@@ -239,7 +239,7 @@ field in the messages:
 - The schema_url field in the InstrumentationLibraryLogs message applies to the
  contained LogRecord messages.
 
-- If schema_url field is non-empty both in Resource\*message and in the
+- If schema_url field is non-empty both in Resource\* message and in the
  contained InstrumentationLibrary\* message then the value in
  InstrumentationLibrary\* message takes the precedence.