subprojects: Update .gitignore for proc-macro2 and syn

Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20250920160520.3699591-2-zhao1.liu@intel.com

subprojects/.gitignore

@@ -17,7 +17,7 @@
 /libc-0.2.162
 /proc-macro-error-1.0.4
 /proc-macro-error-attr-1.0.4
-/proc-macro2-1.0.84
+/proc-macro2-1.0.95
 /quote-1.0.36
 /syn-2.0.66
 /unicode-ident-1.0.12