revert to just base-php tag

we will no longer attempt further PHP upgrades.  Staying at PHP 7.4

docker/app/Dockerfile

@@ -38,7 +38,7 @@ RUN npm run build:${NPM_BUILD_SUFFIX}
 # COMPOSER-BUILDER
 # download composer app dependencies
 # git - needed for composer install
-FROM sillsdev/web-languageforge:base-php-7.4 AS composer-builder
+FROM sillsdev/web-languageforge:base-php AS composer-builder
 ENV COMPOSER_ALLOW_SUPERUSER=1
 RUN apt-get update && apt-get install -y git && rm -rf /var/lib/apt/lists/* \
     && install-php-extensions @composer
@@ -47,15 +47,15 @@ COPY src/composer.json src/composer.lock /composer/
 RUN composer install
 
 # PRODUCTION IMAGE
-FROM sillsdev/web-languageforge:base-php-7.4 AS production-app
+FROM sillsdev/web-languageforge:base-php AS production-app
 RUN rm /usr/local/bin/install-php-extensions
 RUN apt-get remove -y gnupg2
 RUN mv $PHP_INI_DIR/php.ini-production $PHP_INI_DIR/php.ini
 # had to add /wait into prod image so the prod image could be run through E2E tests.
 COPY --from=sillsdev/web-languageforge:wait-latest /wait /wait
 
 # DEVELOPMENT IMAGE
-FROM sillsdev/web-languageforge:base-php-7.4 AS development-app
+FROM sillsdev/web-languageforge:base-php AS development-app
 RUN install-php-extensions xdebug-^3.1
 COPY docker/app/docker-php-ext-xdebug.ini /usr/local/etc/php/conf.d
 RUN mv $PHP_INI_DIR/php.ini-development $PHP_INI_DIR/php.ini

docker/test-php/Dockerfile

@@ -1,4 +1,4 @@
-FROM sillsdev/web-languageforge:base-php-7.4
+FROM sillsdev/web-languageforge:base-php
 
 
 # ----- LINES BELOW COPIED FROM APP DOCKERFILE ----------