Drop now-obsolete oniguruma library

Author: TimWolla

Dockerfile-linux.template

@@ -284,7 +284,7 @@ RUN set -eux; \
 			# https://github.com/docker-library/php/issues/888
 			"linux-headers",
 			# oniguruma is part of mbstring in php 7.4+
-			"oniguruma-dev"
+			if install_pear_pecl then "oniguruma-dev" else empty end
 		else
 			# debian packages
 			if env.variant == "apache" then "apache2-dev" else empty end,
@@ -297,7 +297,7 @@ RUN set -eux; \
 			"libxml2-dev",
 			"zlib1g-dev",
 			# oniguruma is part of mbstring in php 7.4+
-			"libonig-dev"
+			if install_pear_pecl then "libonig-dev" else empty end
 		end ] | sort[] | (
 -}}
 		{{ . }} \