[Github] Remove CMake options from docs CI resetting defaults

The SPHINX_OUTPUT_HTML and SPHINX_OUTPUT_MAN CMake flags are by default
set to ON/True in ./llvm/cmake/modules/FindSphinx.cmake, so we don't
need to set them true again within the CMake invocation.

Author: boomanaiden154

.github/workflows/docs.yml

@@ -62,11 +62,11 @@ jobs:
       - name: Build LLVM docs
         if: steps.docs-changed-subprojects.outputs.llvm_any_changed == 'true'
         run: |
-          cmake -B llvm-build -GNinja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_SPHINX=ON -DSPHINX_OUTPUT_HTML=ON -DSPHINX_OUTPUT_MAN=ON ./llvm
+          cmake -B llvm-build -GNinja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_SPHINX=ON ./llvm
           TZ=UTC ninja -C llvm-build docs-llvm-html docs-llvm-man
       - name: Build Clang docs
         if: steps.docs-changed-subprojects.outputs.clang_any_changed == 'true'
         run: |
-          cmake -B clang-build -GNinja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_SPHINX=ON -DSPHINX_OUTPUT_HTML=ON -DSPHINX_OUTPUT_MAN=ON ./llvm
+          cmake -B clang-build -GNinja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang" -DLLVM_ENABLE_SPHINX=ON ./llvm
           TZ=UTC ninja -C clang-build docs-clang-html docs-clang-man