chore(rstcheck): update config key name

The config for rstcheck changed slightly, it expects ignore_language to
be ignore_languages now.

Signed-off-by: Randolph Sapp <[email protected]>

.rstcheck.cfg

@@ -2,5 +2,5 @@
 ignore_directives = ifconfig
 # ignore the following languages because they require external compilers and
 # snippets in this repo depend on external code
-ignore_language = c,cpp,c++
+ignore_languages = c,cpp,c++
 ignore_substitutions = __PART_FAMILY_NAME__,__PART_FAMILY_DEVICE_NAMES__,__PRODUCT_LINE_NAME__,__SDK_BUILD_MACHINE__,__SDK_FULL_NAME__,__SDK_SHORT_NAME__,__SDK_INSTALL_FILE__,__SDK_INSTALL_DIR__,__SDK_DOWNLOAD_URL__,__LINUX_UBUNTU_VERSION_LONG__,__LINUX_UBUNTU_VERSION_SHORT__,__OPTEE_PLATFORM_FLAVOR__,__RTOS_UBUNTU_VERSION_LONG__,__WINDOWS_SUPPORTED_LONG__,__FEATURINGMATRIX__,__SYSFW_CORE_NAME__,__PCIE_BASE_ADDRESS__,__PCIE_DEVICE_ID__