[BUILD] Add language extras to .gitignore (#4872)

Address an issue caused by
triton-lang/triton@53166ef
after which we will see extra libraries after building from source each
time, such as `python/triton/language/extra/cuda`.

Author: Jokeren

.gitignore

@@ -17,6 +17,9 @@ python/triton/backends/
 !python/triton/backends/compiler.py
 !python/triton/backends/driver.py
 
+# Language extras
+python/triton/language/extra
+
 # Proton
 python/triton/profiler