Rename test-removal.rst

All other rst files don't contain "-" in the file names instead of '_'.
This patch renames test-removal.rst for consistent format on rst files.

TrivialFix

Change-Id: I229870baa1954e1f6b2277318ae5bae332f660ad
diff --git a/doc/source/index.rst b/doc/source/index.rst
index a385111..1264ecc 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -67,7 +67,7 @@
    HACKING
    REVIEWING
    microversion_testing
-   test-removal
+   test_removal
    write_tests
 
 -------
diff --git a/doc/source/test-removal.rst b/doc/source/test_removal.rst
similarity index 100%
rename from doc/source/test-removal.rst
rename to doc/source/test_removal.rst