assignments: fixed undefined labels

* source/compiler_stages/tc_2/goals.rst,
* source/compiler_stages/tc_2/improvements.rst,
* source/compiler_stages/tc_3/code_to_write.rst,
* source/compiler_stages/tc_5/faq.rst,
* source/compiler_stages/tc_5/goals.rst,
* source/compiler_stages/tc_5/primitive_samples.rst,
* source/compiler_stages/tc_8/faq.rst,
* source/compiler_stages/tc_9/samples.rst,
* source/compiler_stages/tc_e/code_to_write.rst,
* source/instructions/coding_style/documentation_style.rst,
* source/instructions/coding_style/matters_of_style.rst,
* source/instructions/coding_style/name_conventions.rst,
* source/instructions/coding_style/use_of_cpp_features.rst,
* source/instructions/coding_style/use_of_foreign_features.rst,
* source/instructions/interactions.rst,
* source/instructions/rules_of_the_game.rst,
* source/instructions/submission.rst,
* source/instructions/tests/tests.rst,
* source/instructions/tests/writing_tests.rst,
* source/intro/history/tiger_2005.rst,
* source/intro/how_to_read_this_document.rst,
* source/intro/why_the_tiger_project.rst,
* source/source_code/project_layout/build_aux.rst,
* source/source_code/project_layout/lib_misc.rst,
* source/source_code/project_layout/src_ast.rst,
* source/tools/bibliography.rst,
* source/tools/gnu_build_system/gnu_build_system.rst,
* source/tools/monoburg.rst,
* source/tools/programming_environment.rst,
* source/tools/valgrind.rst: here.
1 job for master in 46 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #31486
trigger-tc

00:00:46