Remove Mercurial configuration intended for internal use

PiperOrigin-RevId: 372893564

.hgignore

-# Mercurial's .hgignore files can only be used in the root directory.
-# You can still apply these rules by adding
-# include:path/to/this/directory/.hgignore to the top-level .hgignore file.
-
-# Ensure same syntax as in .gitignore can be used
-syntax:glob
-
-# Android generated
-bin
-gen
-libs
-obj
-lint.xml
-
-# IntelliJ IDEA & Android Studio
-.idea
-*.iml
-*.ipr
-*.iws
-classes
-gen-external-apklibs
-*.li
-
-# Eclipse
-.project
-.classpath
-.settings
-.checkstyle
-.cproject
-
-# Gradle
-.gradle
-build
-buildout
-out
-
-# Maven
-target
-release.properties
-pom.xml.*
-
-# Ant
-ant.properties
-local.properties
-proguard.cfg
-proguard-project.txt
-
-# Bazel
-bazel-bin
-bazel-genfiles
-bazel-out
-bazel-testlogs
-
-# Other
-.DS_Store
-cmake-build-debug
-dist
-jacoco.exec
-tmp
-
-# VP9 extension
-extensions/vp9/src/main/jni/libvpx
-extensions/vp9/src/main/jni/libvpx_android_configs
-extensions/vp9/src/main/jni/libyuv
-
-# AV1 extension
-extensions/av1/src/main/jni/libgav1
-extensions/av1/src/main/jni/cpu_features
-
-# Opus extension
-extensions/opus/src/main/jni/libopus
-
-# FLAC extension
-extensions/flac/src/main/jni/flac
-
-# FFmpeg extension
-extensions/ffmpeg/src/main/jni/ffmpeg