[Trivial] Fix rpc type-o in two places

[HowardHinnant]

Thanks for spotting this Nik. I searched for more instances of the same bug and found a second example in the same file.

[codecov-io]

Codecov Report

Merging #2008 into develop will decrease coverage by -0.03%.
The diff coverage is 50%.

@@             Coverage Diff             @@
##           develop    #2008      +/-   ##
===========================================
- Coverage    67.27%   67.25%   -0.03%     
===========================================
  Files          683      683              
  Lines        49231    49231              
===========================================
- Hits         33121    33110      -11     
- Misses       16110    16121      +11

Impacted Files	Coverage Δ
src/ripple/rpc/impl/ServerHandlerImp.cpp	76.34% <50%> (ø)	✅
src/ripple/app/misc/impl/LoadFeeTrack.cpp	81.53% <ø> (-4.62%)	❌
src/ripple/beast/core/WaitableEvent.cpp	87.75% <ø> (-4.09%)	❌
src/ripple/server/impl/BaseWSPeer.h	77.5% <ø> (-3.34%)	❌
src/ripple/core/impl/Stoppable.cpp	92.55% <ø> (-3.2%)	❌
src/ripple/app/main/LoadManager.cpp	73.68% <ø> (-1.32%)	❌
src/ripple/basics/impl/make_SSLContext.cpp	53.5% <ø> (+1.27%)	✅

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[miguelportilla]

👍

[HowardHinnant]

Rebased to 0.60.0-b4

[seelabs]

In 0.60.0-b7