Bump RDoc to 1f93543 (rbs-integrated)

Re-applies the bump originally made in ruby#16940 and reverted in ruby#16978.
The build-side fixes earlier in this branch (extract-gems ordering
plus the `update-deps` filter for bundled-gem extensions) ensure
`rbs` is built and its gemspec is registered in
`.bundle/specifications/` before doc generation runs, so
`require 'rdoc/rdoc'` can transitively activate `rbs (>= 4.0.0)`
through rdoc's runtime dependencies.

Author: st0012

gems/bundled_gems

@@ -37,7 +37,7 @@ ostruct             0.6.3   https://github.com/ruby/ostruct
 pstore              0.2.1   https://github.com/ruby/pstore
 benchmark           0.5.0   https://github.com/ruby/benchmark
 logger              1.7.0   https://github.com/ruby/logger
-rdoc                7.2.0   https://github.com/ruby/rdoc bc0baee787609f2205e8f1103f3e1d36b923184a
+rdoc                7.2.0   https://github.com/ruby/rdoc 1f93543615928b6d45357432f16ec6006e2d8b1e
 win32ole            1.9.3   https://github.com/ruby/win32ole
 irb                 1.18.0  https://github.com/ruby/irb
 reline              0.6.3   https://github.com/ruby/reline