[Github] Disable counting tests to code summary

Co-authored-by: Gliniak <153369+Gliniak@users.noreply.github.com>

Author: has207

.gitattributes

@@ -11,3 +11,4 @@
 src/**/shaders/bytecode/** linguist-generated=true
 # Preserve CRLF for generated shader headers
 src/xenia/gpu/shaders/bytecode/d3d12_5_1/*.h text eol=crlf
+src/**/testing/** linguist-detectable=false