docs: fix regression that broke intended meaning of compiler variables note

In commit 58c2aeb5e4, an asterisk used to
indicate "see note at bottom" was doubled up into an "italicize this
paragraph", which didn't contextually make any sense.

See: https://github.com/mesonbuild/meson/pull/12674#issue-2057666653

docs/markdown/Reference-tables.md

@@ -377,7 +377,7 @@ machine](#Environment-variables-per-machine) section for details.
 | nasm          | NASM     |           | Uses the C linker                           |
 
 *The old environment variables are still supported, but are deprecated
-and will be removed in a future version of Meson.*
+and will be removed in a future version of Meson.
 
 *changed in 1.3.0* Paths with spaces were split unconditionally to extract
 components such as the [path to Ccache](Feature-autodetection.md#ccache),